MPG to expect

[shavergator]

Just curious about miles per gallon. What can you expect to get on a Ford V-10. Mine is in a 34 foot ( 2000 ) Monaco Monarch. I know there are many factors that affect miles per gallon, but what is a good average to expect averaging 60 on the highway. And what would a comparable diesel average ?

[Mc2guy]

YRMV, but it would seem that 6.5-8.0 mpg would be the norm for this engine and body size.  I have been averaging about 7.5 in a 2009 Winnebago Sightseer 35J.  I have not owned a diesel, but most seem to report 9-10 for an equivalent model. 

[DonTom]

Just curious about miles per gallon. What can you expect to get on a Ford V-10. Mine is in a 34 foot ( 2000 ) Monaco Monarch. I know there are many factors that affect miles per gallon, but what is a good average to expect averaging 60 on the highway. And what would a comparable diesel average ?

My guess is that you will average about 7 MPG at 60 MPH. If it were a diesel, I would expect you would get around 10 MPG.

                                             

    -Don- SSF, CA

[FrontrangeRVer]

We had a 1999 Holiday Rambler Vacationer 36' motorhome with the V-10, and we got 6.0 - 6.5 mpg.  I wasn't easy on the gas pedal either, so you could possibly get 7.....

[RV Roamer]

I'd say 7.5-8.0 if you have a light foot, around 6.5-7.0 if not. Towing a car typically impacts a gas chassis by up to 0.5 mpg., so those numbers might increase if you do not have a toad.

[Wizard46]

My 2002 Brave 34' gets about 6.5 to 7 on Florida Interstates with my driving. I could probably get a little better if I slowed down, but probab,y not more than 7.5 and then I would be afraid of getting run over !!!!!

[sheltie]

My 2002 Brave 34' gets about 6.5 to 7 on Florida Interstates with my driving. I could probably get a little better if I slowed down, but probab,y not more than 7.5 and then I would be afraid of getting run over !!!!!

Not trying to throw fuel into the fire, but I have a different question.  Why, after one has spent a very significant amount of money to buy a mid/big rig would anyone worry about the mpg?  You know going in that you will get a small range of mpg, regardless of the gasser engine, so why worry?  Even if one increases mpg by 2 mpg (unlikely), the saving per tankful is insignificant when considering how much you originally paid for your rig.  Don't obsess, just enjoy.

[DonTom]

Even if one increases mpg by 2 mpg (unlikely), the saving per tankful is insignificant when considering how much you originally paid for your rig.

There are other reasons. One that's important to me is how far the vehicle can go on a tank of gas. There are still many routes  that are more than 100 miles between gas stations and then when you get to the next gas station, it's closed for whatever reason. That 2 mpg would get you another 100 miles with a 50 gallon tank.

-Don- SSF, CA

[shavergator]

Thank you all for your ideas. I would say 7mpg is about right.  How much change would you expect when running the generator ?

[DonTom]

Why, after one has spent a very significant amount of money to buy a mid/big rig would anyone worry about the mpg? 

Because after spending "a very significant amount of money to buy a mid/big rig" they might not have enough money left to make the payments if they get a poor MPG .

-Don- SF, CA

[RV Roamer]

How much change would you expect when running the generator ?

A typical generator will consume 0.5 gal per hour at about 50% load. That's probably more than your actual load if running just one a/c. The genset manual will likely have an estimated fuel consumption.

[tallyo]

There are other reasons. One that's important to me is how far the vehicle can go on a tank of gas. There are still many routes  that are more than 100 miles between gas stations and then when you get to the next gas station, it's closed for whatever reason. That 2 mpg would get you another 100 miles with a 50 gallon tank.

-Don- SSF, CA

 I learned a long time ago never to see how far I could stretch a tank of fuel..... Generator won't run when tank is below 1/4, if yer ever stuck someplace without a hook up you may need some fuel just to beat the heat. If yer ever in a campground that loses power for any time period .. well you get the drift.....

I always start looking for a fuel stop when I get near the 1/2 tank...... I call my travels a "half tank trip"

[scottydl]

I always start looking for a fuel stop when I get near the 1/2 tank...... I call my travels a "half tank trip"

And I don't know about anyone else, but when my gauge reads at the 1/2 mark, I really only have about 1/4 tank left anyway!  Every vehicle I've ever had has artificially stayed on/near "Full" longer than it should, then the needle drops like a brick.  Of course the RV has many more reasons why it's not a good idea to potentially run out of gas while who-knows-where out on the road.

[Mc2guy]

My gauge seems to have five 15 gallon increments.  Past F to F is 15 gallons, Full to 3/4 is 15 gallons, 3/4 to half is 15 gallons, and half to 1/4 is 15 gallons.  I have tested each increment with the scan-gauge and with a fill-up and they seem spot on.

[tallyo]

And I don't know about anyone else, but when my gauge reads at the 1/2 mark, I really only have about 1/4 tank left anyway!  Every vehicle I've ever had has artificially stayed on/near "Full" longer than it should, then the needle drops like a brick.  Of course the RV has many more reasons why it's not a good idea to potentially run out of gas while who-knows-where out on the road.

So much depends upon the shape of the fuel tank. If it's fatter at one end ( top or bottom) then the readings can be affected. I always find the guy who says he's getting many mile per gallon  is figuring at the 1/2 tank reading or is using the MPG reading off the dash board and is not using actual gallons used at refill time.....

After so many years and so many fill ups, I just keep pumping , paying and enjoying the ride....

[scottydl]

Not trying to throw fuel into the fire, but I have a different question.  Why, after one has spent a very significant amount of money to buy a mid/big rig would anyone worry about the mpg?

I always keep track of mine (1) because I'm curious, (2) because I like to see how different circumstances affect or don't affect the mileage so I *can* maximize (even by just a little) if reasonable, and (3) because if the average ever REALLY decreases it can give forewarning of a mechanical problem that might otherwise go unnoticed and lead to something worse.  Just a few reasons. 

[DonTom]

I learned a long time ago never to see how far I could stretch a tank of fuel..... Generator won't run when tank is below 1/4, if yer ever stuck someplace without a hook up you may need some fuel just to beat the heat. If yer ever in a campground that loses power for any time period .. well you get the drift.....
I always start looking for a fuel stop when I get near the 1/2 tank...... I call my travels a "half tank trip"

Is that the generator won't start below a quarter tank fairly standard in RVs? I had no idea that they made RV's that idiot proof. 

Another reason to want a lot of gasoline in the tank at all times is for the fuel pump. The gasoline helps keep the fuel pump cool and it will last longer when it's all in the gasoline. It runs hotter when the tank is near empty. To have a fuel pump replaced can be an expensive job in a RV.

BTW, the best MPG I ever got in my old 22 foot class C (1978 400 CID  junk small block, but with MPFI <modified by me> ) was when I was driving in Yellowstone all day with very low speed limits. Got just over ten MPG at an average of 30 MPH or so.

The modification I did was from here.

-Don- SSF, CA

[RV Roamer]

Is that the generator won't start below a quarter tank fairly standard in RVs?

Yes, but the nominal "1/4 tank" can have a wide variance, depending on the whim of the guy who installs the generator fuel line into the tank. Consistency is NOT a hallmark of RV production.

[DonTom]

Yes, but the nominal "1/4 tank" can have a wide variance, depending on the whim of the guy who installs the generator fuel line into the tank. Consistency is NOT a hallmark of RV production.

That's nice to know as I had no clue about that and I probably would have tried to fix something that's not broken if I ever let my gas tank get that low.

BTW, something I was curious about. Where's the fuel pump located for the generator? Is it in the generator itself, or somewhere on the fuel line, or in the gas tank? Or again does it depend on who designed the RV?

-Don- SSF, CA

[Kirk]

We have owned our Ford V-10 chassis motorhome now since it was new ten years ago. At first we were getting about 7 mpg and the difference when towing our Ford Ranger and not towing was hardly detectable. After about 18 months of this we had the complete Banks upgrade put on with the TransCommand unit for the transmission. This system greatly improved our performance and since we keep the right foot light, that increase in power has also gained us a significant improvement in mileage. We now typically get around 8 mpg, and 8.5 is not uncommon and that is always towing, because we are fulltimers.

[RV Roamer]

Where's the fuel pump located for the generator?

Probably depends on the generator make and model. Since the generator is designed and installed separate from the chassis and fuel tank, I assume it will have its own fuel pump rather than in the tank, but it could be external (on the fuel line) or bolted to the genset itself.

[Lou Schneider]

Usually the generator is supplied as a package, complete with enclosure,etc.   The fuel pump is part of this package.  Look for a little square module in the fuel line.

[DonTom]

Usually the generator is supplied as a package, complete with enclosure,etc.   The fuel pump is part of this package.  Look for a little square module in the fuel line.

You mean the fuel line after it gets into the generator? I think I would have to take the generator out to find it. But it must be there, because I could not find it anywhere on the fuel lines under the RV. I checked a few days ago when I was last at my Reno home.  I will have to look at the generator manual again.

                                                                                       

-Don- SF, CA

[mdbass]

I agree with the "never let it get below a 1/2 tank" rationale. Not championing for diesels; but I had one gas rig and that cured me-6.5 mpg tops! All my diesels have gotten 10-11 to the gallon. I understand the rationale for wanting to know mpg, but I also agree it's sorta mox nix after a while. I figure it costs me around $100-$125 a day to RV-and that's driving. (It probably got higher when diesel went to $4.00 a gal) We've been down this road many times before. Today its even more topical-have you checked the cost of hotels and eating out lately? Obviously, I love our coach, but I'm not trading for a hotel room anytime soon. Our opinion-go with a diesel with a slide. We fulltime now; but used one every other weekend or so for years and it worked just as well.

[kevin]

10-11mpg WOW

[maryland-david]

wll I have a pretty big Cummins and weigh around 50,000# with Toad and get between 6-7MPG. I thought that I would get better than that and I have a light foot.

[mdbass]

We dropped to 9.5 - 10 mpg last trip- 1300 miles with a toad. It can be done. BTW we are governed to 1850 rpm-(65 mph) and average somewhere in the mid 50 mph range according to our gps. We stay in the right (granny) lane and mosey along. The return in fuel savings more than justifies it. If you want to try this, make sure your mechanic adjusts the rail pressure when he governs the rpm. That way you don't lose your low end grunt.

[mdbass]

Maryland David-We have the small Cummins in a HR Endeavor. We also weigh a lot less than you. Geez-we're barely pushing 30,000 pds. Also; if you have a newer RV, it's probably controlled by several computers (like the DDEC system in Detroit engines). It really behooves you to use the cruise as much as possible if this applies to you as it is designed to maximize fuel consumption. You can also get a wealth of information from the computers (your mechanic can download it or you can purchase the adaptor to connect your PC or laptop to the onboard computer (via the PROM). Believe me, you won't be able to digest it all. It can help you with your fuel consumption.

[kevin]

Not to start a fight, but how on earth do you not get run over on the interstate? you must be doing30 on the big hills too? I guess if that is what ya gotta do to get 9-11mpg then so be it,but I just can't run that slow

[maryland-david]

Maryland David-We have the small Cummins in a HR Endeavor. We also weigh a lot less than you. Geez-we're barely pushing 30,000 pds. Also; if you have a newer RV, it's probably controlled by several computers (like the DDEC system in Detroit engines). It really behooves you to use the cruise as much as possible if this applies to you as it is designed to maximize fuel consumption. You can also get a wealth of information from the computers (your mechanic can download it or you can purchase the adaptor to connect your PC or laptop to the onboard computer (via the PROM). Believe me, you won't be able to digest it all. It can help you with your fuel consumption.

Yeah even with my extra 20,000#, I was expecting 7-9MPG. I have over 2 million miles driving big diesels and I have always gotten great fuel mileage. I just have not found a sweet spot for my combination. Of course I think that gap in the Allison 6 speed is too big. I ran 13 speeds and 18 speed transmissions most of the time. I am probably even dating myself but even drove a 6x4. At 65-70MPH I am near 6MPG. At 55-60MPH I am closer to 7MPG.

[RV Roamer]

I'm in between you two. We run at 32,700 lbs plus a 5000 lb toad for a total of 37,700 on a Cummins ISL 370. Cruising steadily at 63-64 mph (about 1650 RPMs) on an Interstate, we get 8.1-8.4 mpg. But if I try to do the same on a two lane road, the inevitable variations in speed due to traffic and towns put our average closer to 53 than 63 and the mpg drops to 7.2-7.6, no matter how light I try to keep my foot.

I find that I am not being run over at that speed, far from it. Some people pass me but others seem to be keeping around the same space. I even pass a few.

[taoshum]

Our last 3000 miles to Nashville and back averaged 8.9 MPG.  I set the CC at 65 on the big highways and about 60MPG on the smaller hiways. A headwind makes a large difference compared to a tailwind during the trip.  We were towing a Jeep wrangler, our weight was about 27,000 lb counting the Jeep and the engine is a small cummins diesel with a 5 spd Allision AT.  I try to keep the tank above the 1/4 level.  It was hot, so we ran the generator most of the time to run the house a/c.  I did vary the tire pressure (see the other thread) as experiments to improve the ride, plus we have a large elevation change to consider... 400 ft above MSL in Tennessee and 7800 ft elevation at home.  I really don't know what the MPG would be for a flat, smooth hiway with no wind, without a/c and a steady 60 MPH... maybe 9-10 mpg?

After a while, the only reason I even look at it is to detect a major leak or problem with the engine or drive train.

Very interesting thread.  Thanks.  Gary.

[BernieD]

David

At the last Cummins seminar I attended the presenter said that the "sweet spot" should be around 1650 RPM. I've tried keeping the coach in that area, 1625-1660, and my cruise is set at 62-63 mph. I've averaged tank fills of about 8.75-9.0 mpg and day figures of up to 10. A lot depends on wind, terrain and traffic.

[Marsha/CA]

Bernie, we are getting just about the same as you with a cat engine.  I knew about the "sweet spot" and it seems to work.   Tim keeps meticulous records on the coach...(well now that I think about it he keeps meticulous records on everything  ) and we seem to run fairly consistent.  However on that Gaspe' Peninsula drive we averaged 6.7 mpg something.  Those 14-15% grades really made a difference.

Marsha~

[maryland-david]

David

At the last Cummins seminar I attended the presenter said that the "sweet spot" should be around 1650 RPM. I've tried keeping the coach in that area, 1625-1660, and my cruise is set at 62-63 mph. I've averaged tank fills of about 8.75-9.0 mpg and day figures of up to 10. A lot depends on wind, terrain and traffic.

What size Cummins do you have? Do you have the Allison tranny? If so is this only 5th gear? I have not put many miles with an automatic transmission so I just let it pick its own gear. In my tractor trailers I always tried to keep the rpm at 1600, but due to the weight of 80,000# or so, it was also necessary for torque. However in 6th gear at 65MPH in my MH, I am way under 1600RPM. Maybe I'll try downshifting and see if that makes a difference.

[RV Roamer]

However in 6th gear at 65MPH in my MH, I am way under 1600RPM.

Way under??   You've probably got a larger, torquier engine than I do (an ISM or ISX?), but most Cummins configured for RVs are geared to hit 60 mpg as it shifts into 6th gear at about 1550-1600 rpms.

[BernieD]

David, I have the 400 ISL. IIRC at the seminar, there were some complaints from owners of the 500-600 hp engines about being able to keep the speed down and the RPMs up. Yes, keeping it in 5th gear was tossed out as an option. You'd have to play with it and see. Do you have an instant or rolling average mpg readout? That could help finding the sweetspot for your engine. That's what I had done and the seminar confirmed my results.

[RV Roamer]

Guys I know with late model American Heritages (your size of rig) are also seeing 6.x mpg.  2007 and newer engines are also running lower in mpg than those of 2003-2006, at least in the larger engines. Not so much difference at the smaller end (ISB & ISC).  Of course, every year the coaches got longer and heavier too!

[kevin]

I find that I am not being run over at that speed, far from it. Some people pass me but others seem to be keeping around the same space. I even pass a few.

On our trip to florida and back I never passed anyone while going 65 or 70, I was passed by everyone but some of the poor ole governed truckers... oh well I seem to be getting 6-6.5 running the speed limit.

[edit]fixed broken quote[/edit]

[maryland-david]

Way under??   You've probably got a larger, torquier engine than I do (an ISM or ISX?), but most Cummins configured for RVs are geared to hit 60 mpg as it shifts into 6th gear at about 1550-1600 rpms.

Gary, I am going to have to check, but I am definitely at least 200-250 under 1650RPM. I understand with the bad fuel mileage of the 2007+, I believe this is due to the DPF. The regens on the DPF diesels do nothing but basically poor raw diesel into the exhaust. My 2008 Duramx diesel gets 2-4MPG less than a nopn DPF diesel. I have just assumed that the Allison tranny was smart enough to choose the right gear. I am going to switch into manual mode and see if my mileage increases from there.

Bernie, I do have the instant MPG gauge, even though I have never thought that they were very accurate, but it is a starting place nonetheless.

On this subject, has anyone noticed changing to synthetic oil in the engine making any noticeable difference in fuel mileage. I only have about 70,000 miles on my coach, so it is not too late to switch to synthetic.

Thanks,

[Mc2guy]

I might be a bit off topic as I drive a gas engine motorhome, 2009 F53 chassis with the 6.8L V10.  I just returned from a three week 5200 mile trip from Virginia to Idaho and back.  I would run between 62-66 mph with the generator running 80% of the time and returned 7.3 mpg for the trip. 

I saw tanks as high as 8.3 running at night in the high flats of Wyoming, and as low as 5.8 mpg heading into the wind through Kansas.

[RV Roamer]

David, What engine do you have? I'm guessing a Cummins ISX or maybe a Cat C15? A check of the peak torque range on those engines does indeed show that the sweet spot is closer to 1450 than 1650 rpms, so you probably can cruise at 65 mph at something like 1450 rpms. I stand corrected!

[maryland-david]

David, What engine do you have? I'm guessing a Cummins ISX or maybe a Cat C15? A check of the peak torque range on those engines does indeed show that the sweet spot is closer to 1450 than 1650 rpms, so you probably can cruise at 65 mph at something like 1450 rpms. I stand corrected!

Gary I have a 2003 Cummins 500. I always just called the an N14e, which I believe stands for 14 liter. Seems like in 2003 it may have been ISM??

[maryland-david]

I might be a bit off topic as I drive a gas engine motorhome, 2009 F53 chassis with the 6.8L V10.  I just returned from a three week 5200 mile trip from Virginia to Idaho and back.  I would run between 62-66 mph with the generator running 80% of the time and returned 7.3 mpg for the trip. 

I saw tanks as high as 8.3 running at night in the high flats of Wyoming, and as low as 5.8 mpg heading into the wind through Kansas.

That is great mileage.

[maryland-david]

Gary I have a 2003 Cummins 500. I always just called the an N14e, which I believe stands for 14 liter. Seems like in 2003 it may have been ISM??

I just assumed since my last 500HP Cummins from the 1990's was an N14e that this one was also, maybe it is an ISX, I'll check and get back to you.

[BernieD]

David

It is probably the ISM. The ISX was up around 600hp.

[RV Roamer]

According to Cummins the current ISX's are 14.9L and may be configured anywhere from 385 hp to 600 hp (usually 525 or 600 in an RV). But I suspect you are right that in 2003 they were using an ISM rather than the ISX. ISMs are 10.8L and can be anywhere from 280 hp to 500, but in RVs they are usually 450 or 500 hp, since the ISL delivers 370-425 hp. Peak torque can be either 1450 or 1550 on an ISM, depending on the configuration.  David seems to be running at 1450. That's why I suspected an ISX, but an ISM is a possible too.

http://www.cummins-sp.com/document_library/Spec_Sheets/Engines/ISM_500.pdf

[maryland-david]

According to Cummins the current ISX's are 14.9L and may be configured anywhere from 385 hp to 600 hp (usually 525 or 600 in an RV). But I suspect you are right that in 2003 they were using an ISM rather than the ISX. ISMs are 10.8L and can be anywhere from 280 hp to 500, but in RVs they are usually 450 or 500 hp, since the ISL delivers 370-425 hp. Peak torque can be either 1450 or 1550 on an ISM, depending on the configuration.  David seems to be running at 1450. That's why I suspected an ISX, but an ISM is a possible too.

http://www.cummins-sp.com/document_library/Spec_Sheets/Engines/ISM_500.pdf

Well Gary this is what I get for assuming. I had a Cummins 500 in a tractor trailer and it was a N14e, I assumed that's what mine was. I looked at the data plate on the engine today, boy was that a pain to get to! It is indeed an ISM rated at 500HP at 1800RPM. Peak torque is at 1200RPM. I took it out on the road and at 65MPH I am between 1050-1100. I will try 5th gear and 1200RPM and see if that increases my fuel mileage at all for a trip and rerport back.

Any known issue or known problems with the ISM's?

[RV Roamer]

No issues that I know of.

[mdbass]

Not to start a fight, but how on earth do you not get run over on the interstate? you must be doing30 on the big hills too? I guess if that is what ya gotta do to get 9-11mpg then so be it,but I just can't run that slow

No offense taken-us "non banks" 235 hp DP guys see 30 on hills occasionally. Like I said, we stay to the left. Let me tell you I'd love a 400-600 hp motor-but this is what I could afford. I may have the governor adjusted or purchase a Banks kit eventually.

[maryland-david]

No offense taken-us "non banks" 235 hp DP guys see 30 on hills occasionally. Like I said, we stay to the left. Let me tell you I'd love a 400-600 hp motor-but this is what I could afford. I may have the governor adjusted or purchase a Banks kit eventually.

If you are in the US, I hope that you stay to the right, not the left! I would be very haqppy with your fuel mileage and don't worry about your speed! Just try n ot to be a hazzard.

On my previous post of RPM's, that was a typo, that was my RPM at 55MPH in 6th gear. Most of the time it wouldn't let me slow down to 55 in 6th gear, but I got it to do it a couple of times. At 65MPH I am about 1375RPM. I may try a trip at 60MPH in 5th gear and see if that improves my mileage at all.

[HJohsens]

I have a 1995 Safari with an 8.3 liter Cummins that I have been getting 7.5 MPG so far. My driving has ranged from 55 MPH in the Peoples Republik of Kalifornia (where I live) to 75 or 80 MPH in Texas. I am not consistent at all. I have just changed the intake air system so that it is less restrictive and I hope to get better MPG next week when we drive to LA.

 My experience is that I was lied to regarding what MPG I could expect when I bought it (which I fully expected) and that most RV'rs will pad their mileage when talking to others, including other RV'rs.

 I was told (or perhaps "sold" to expect 10 MPG or more) but my 7.5 mpg is a grand total of over 6000 miles driven divided by the amount of fuel pumped into the tank. I have burned out the tank to near empty at times and spent a huge amount of time filling the tank to make sure I am full-up and topped off.

 With diesels it is important to know that the diesel fuel foams up significantly when being pumped. For this reason before filling my tank I will use the levelling jacks to raise the filling corner of the tank to the highest point (so that the foam will vent out through the filler neck). I will also spend the time waiting for the foam to settle out and fill the tank to capacity.

 In my experience I have found that depending on climatic conditions where I am filling I have had the pump shut off when I have just over 3/4 of a tank full.     

[DonTom]

"75 or 80 MPH in Texas."

Expect a lot of forum members here to chew you out for going at such speeds in a RV!

I once mentioned going 75 MPH in my small 22 foot RV on a rather  empty Colorado interstate freeway ( where the speed limit was 75 MPH) and boy, did I get jumped on here in this forum!

-Don-  SF, CA

[taoshum]

Why do you care so much about getting the tank full?  For me, I have to stop every 300 miles anyway for a break or I just get tired and stop for a while, sometimes several days...  anyway I have plenty of chances to fill the tank... even if it goes to 3/4 or whatever, I don't care... besides it's less weight to carry.  The only time I get concerned is if we are stopping someplace without electricity and I want to make sure the gen/set has plenty of fuel.

It's obviously up to you but it seems extreme to lower the jacks to get a foam free fill?

my 2 francs.  thanks, G.

[taoshum]

I forgot to mention... my long term average is about 8.5 but we "only" have 300Hp and the only time I see 75 is going downhill when I can see another uphill coming right away and I don't want to get runover by the big truck that is right behind me. LOL, whew.  Thx, G.

[RV Roamer]

My sentiments as well.  We seldom feel the need to cover maximum miles or see how far we can get on a tankful.  Relax and enjoy is our motto.

[DonTom]

Why do you care so much about getting the tank full? 

It helps keep the fuel pump in the gas tank cooler so it will last longer. It's also better for the tank to keep it full as much as possible to prevent rust from forming.

-Don- SSF, CA

[Mark R.]

Weight does not effect MPG all that much unless you have to travel uphill both ways, this link is worth looking at and printing it is great for arguments like this one. Enjoy,

http://www.holtrv.com/pdf/understanding.pdf

[GKman]

We just finished a 2600 mile trip from Missouri to Utah and Santa Fe with a 5.9  (360) gasoline 1999 Dodge conversion van pulling a 23' Rockwood fiberglass over aluminum stud trailer with a GVW of 4660 (if we had it loaded to factory specs).  Average mileage was 8.3 mpg with the worst on I-70 at 70 mph of 6.9.  Fuel cost was $0.32/mile.  Dodge has a 3.55 rear end and was driven with the OD locked out.  A lot of shifting down to 2nd. I think gearing around 3.9 would eliminate a lot of the down shifting.  Nice, comfortable, dependable van with room in the back for the 4-wheeler for about 1/2 of it's Cash-for-Clunkers value, got the job done.

[HODAK1172]

I just purchased a 08 f350 powerstroke w/ 4:10 gears last week. I love the truck and the power is great. I got rid of my gas 2500 Dodge and was expecting a huge gain in MPG. However, thats not the case. I tow a 09 Sydney Outback 5er, around 10k lbs. I just went about 2 hrs from my house and averaged 9.5 mpg towing. City driving, unloaded, I am at 13.5. This is my first Diesel and want to know how these numbers stand compared to others. My gasser was getting 8 towing and 12 city, unloaded. At least I have a little bit of a gain!!!

[taoshum]

My son has a F250 that gets 17 town and 20 hiway unloaded and he drives it hard.  It's a 2004 model, and, he's had it modified to have even more power/torque than stock, so it would probably get better MPG if it were stock. FWIW.

[Bobandpamlemay]

I drive a 2008 F250 with diesel and get fairly decent mileage based on this thread. Unloaded in the city I get about 12 mpg on average. On the highway with my 5er I get between 17 and 18 if I keep it on cruise at a legal speed. With my 2009 Komfort trailer at about 12000 lbs, I get between 9 and 10.5, again with cruise on at a legal speed. Strangely enough, I get better mileage with my new 5er at 12,000 lbs than I did with the travel trailer I traded in at 8,000 lbs. Must be the aerodynamics of the new trailer.
A curious question......do the wind deflectors I see on the roof of some pickup help?

Bob

[RV Roamer]

The newer diesels took a  hit to fuel economy as a result of new pollution measures, so a late model diesel will get poorer mileage than an '04. Ford in particular seems to have lost mpg when they changed from the venerable 7.4L Powerstroke to the new 6.0 and then 6.4L engine.

[RV Roamer]

A curious question......do the wind deflectors I see on the roof of some pickup help?

The short answer is "no, probably not".

Long answer: A properly designed wind deflector could make an improvement, perhaps a major  one, but it would have to be set up in a wind tunnel and designed for the air flow around your particular rig. The chances of buying an off-the-shelf deflector, setting it up by eye, and getting much improvement are slim at best.  I am reminded of the ventilated truck tail gates that were the rage for awhile. Seemed obvious they would allow a better air flow and improve mpg, but for most trucks it was later shown that they either did nothing or even hurt the mpg slightly. A truck bed cover, on the other hand, was found to slightly help aerodynamics.

[Bobandpamlemay]

Thanks Gary for your response. Just my luck to buy a 2008 F250 and get less mileage. I undestand that when the filter gets cleaned, I lose about a gallon of diesel fuel. Not good and the EPA stuff cannot be disconnected by anyone I know.
Thanks also for the info on wind deflectors. I see them often and have wondered if they were of any value.

Bob

[taoshum]

Thanks Gary for your response. Just my luck to buy a 2008 F250 and get less mileage. I undestand that when the filter gets cleaned, I lose about a gallon of diesel fuel. Not good and the EPA stuff cannot be disconnected by anyone I know.
Thanks also for the info on wind deflectors. I see them often and have wondered if they were of any value.

Bob

There are "folks" around that can make "improvements" using a different chip and what not.  It's risky though in terms of your warranty and would probably affect the emmissions from the engine in a non-eco/epa way so I guess it's kinda a catch-22.  Getting more mpg would seem to reduce the emmissions per mile though but that's not what they measure.

[Mc2guy]

In theory the conversion to ULSD will only lower efficiency by 1-2%, not enough to notice.  However, in practical application, I am guessing there is something else going on with the engine tuning to reduce the overall efficiency.  Perhaps the reduced lubricity of the lower sulfur fuel is causing OEMs to run a bit richer?  Not sure, but the fuel itself has 99% of the btu's in the old fuel, so it has to be something else causing the efficiency drop that folks are noticing.

[RV Roamer]

ULSD is only a very small piece of the mileage decrease that occurred on diesel engines produced after 1/1/2007. Much more stringent emissions requirements went into effect as well,  with a required 50% reduction in NOx and hydrocarbons and 90% reduction in diesel particulate matter (DPM). These lead to substantial changes in the engine design, including the use of a regeneration cycle  in most engines to burn off DPM and the addition of EGR valves (no more free breathing crankcases). ULSD helps meet the mew emissions requirements by eliminating much of the sulfur at the source, but that's just one piece.

And further reductions will occur in 2010.

[catdozerman]

I recently purchased a 96 holiday rambler 33ft. We have traveled from lower canada, new york,penn.,west virginia, ohio, indiana, kentucky,and tennessee loaded down pulling a 19 ft. boat . I try to stay around 65-68 if i can. Hard to maintain in the mountain states, drops down to 40mph at times. I seem to always get around 6-7 mph reguardless. But i do seem to have a heavy foot at times.

[EandL]

We have a 3500 GMC pick up with a golf cart in the box and pull a 32' Jayco travel trailer and we get about 16 MPG according to the on board computer.

[BigLarry]

We just got back from a 7700 mile trip to the Northwest, of which 5500 was pulling the trailer.  Lots of mountain passes and some very high winds at times.  The overall average for the trip was 12.1mpg.  The truck will get between 18 and 20 mpg when not pulling the trailer.  The poorest milage we got was about 9.6 when driving between Boise, ID and Cortez Colorado with a high headwind.  It's kind of hard to figure loaded and unloaded fuel use because I have a 100 gal fuel tank, so each tank full is used loaded and unloaded.  The weight of our whole rig loaded is about 15000 lbs.

I agree that the newer Diesel trucks have very good performance, however their fuel consumption is definitely less than the earlier models.  I have a friend who had an 03 Chevrolet that got consistently better fuel mileage than mine pulling similar loads.

[WhiteEagle]

Somewhat of comparison - just put on 2000 miles on 2007 Winnebago Voyage 35A - Northern WI, to Columbus OH, North thru MI over Mackinack bridge, back to Green Bay...very windy, seemed like headwind 80% of the time........ first trip in it.. held at 65 on freeway/innerstate, and 55 on all state 2 lanes - on the rolling hills used cruise most of time except when it would drop out on  inclines and then left on "haul/tow" until level road area again (this whole area doesn't have much for terrain... some rolling hills but nothing major).... got 7.4 total... BUT....taking off .5gal/hr for hours that generator was running, got 8.1mpg for total trip...
Now have baseline - hoping for better.... probably shouldn't hold it at 65-66 all the time - even for some of the rolling knolls in the great lakes area.

[FrontrangeRVer]

got 8.1mpg for total trip...

WOW!  That's great!  I've got 23,500 miles on my unit (same as yours), and I haven't even gotten close to 8 mpg!

[WhiteEagle]

Guess I didn't have any personal benchmark but have been reading about the 6.5 - 8 range for expectation and experiences of many... glad I held it at speed limit (+1mph) just to get benchmark and see if I could actually be satisfied staying down to that speed..... didn't seem bad and guess i can relax and enjoy after all......
Will likely see if I can build up 3-4mph prior to inclines and maybe let off a little on the crests - can likely stop the drop down much of the time  ... should have mentioned I was not towing anything ....
If the generator estimate of .5 gal/hr running is applicable to my 5500 Onan, the appears I should be satisfied first data in should be representative and believe I can help it do better if and when i think about it.......

[Mc2guy]

Guess I didn't have any personal benchmark but have been reading about the 6.5 - 8 range for expectation and experiences of many... glad I held it at speed limit (+1mph) just to get benchmark and see if I could actually be satisfied staying down to that speed..... didn't seem bad and guess i can relax and enjoy after all......
Will likely see if I can build up 3-4mph prior to inclines and maybe let off a little on the crests - can likely stop the drop down much of the time  ... should have mentioned I was not towing anything ....
If the generator estimate of .5 gal/hr running is applicable to my 5500 Onan, the appears I should be satisfied first data in should be representative and believe I can help it do better if and when i think about it.......

I believe the generator estimate is OK for an Onan 5500 at half load, which would be around 23 amps.  My experience shows the "average" consumption of my Onan is around 0.3 gal/hour, although I have high efficiency A/C units that only draw around 9 amps per unit.

[tkhattabaugh]

My Excursion has the V10 and I get 7.5 pulling a 31' TT.  When I'm not pulling, I get 14.

[melvonnar]

I was setting at the gas pump gassing up; a man that was gassing his car in the next lane asked me how many MPG I got; on that thing; I said about 28 and never cracked a smile, I was pulling a toad; I assume he was referring to the toad; he sure had a strange look on his face when I told him that.

[tkhattabaugh]

I was setting at the gas pump gassing up; a man that was gassing his car in the next lane asked me how many MPG I got; on that thing; I said about 28 and never cracked a smile, I was pulling a toad; I assume he was referring to the toad; he sure had a strange look on his face when I told him that.

I love it

[Geoff_T]

Hi

It's still early days in my 1996 Ford E350 V8 powered Fleetwood Jamboree Searcher, but I get the impression it's doing around 10mpg at freeway speeds of around 55 to 60mph.

I recently fitted a vacuum gauge (I will post how on the Tech Tips page in the future) as I had these in my UK motor homes. Ths quickly taught me to change down on inclines and never use cruise control or overdrive (unless on a long gentle downhill). It's defintely better to shift down on inclines and let the engine rev, rather than slog up the incline with the right foot down to the floor. The transmission would down shift eventually anyway!

I have a feeling that keeping the needle in the gauge's green region has added several more miles per gallon, indeed I think my RV is getting better gas mileage than my 1989 Mercedes Benz 560SL with its honking great V8 motor!

 

[melvonnar]

Best answer yet:
petal to the medal= 3 to 4 MPG
light feather foot= 8 to 10 MPG

[Mark R.]

This thread needs to be interrupted with a feel good sanity post.

My DP gets 11 MPG solo, 10 with toad at 60 MPH, now for the feel good part, my boat gets 1.2 MPG at 10 MPH and 4.5 gallons per mile at 20 MPH!!!

Feel better about 7.5 MPG now?

[DonTom]

now for the feel good part, my boat gets 1.2 MPG at 10 MPH and 4.5 gallons per mile at 20 MPH!!!
Feel better about 7.5 MPG now?

Not until you tell me what MPG your boat gets when going the same direction as the current. Will that be worse than a RV going downhill? 

-Don- SSF, CA

[Mark R.]

 Will that be worse than a RV going downhill?  I assume you meant uphill.
I think my boat does get worse MPG at 10MPH then my coach does going up hill with toad, and the hill ends in a few minutes but the river is long so the MPG stays bad  as long as its running.

[mrschwarz]

The only long trip I have made showed me 10 mpg on the engine computer. That was driving all day on the interstate. When I go on shorter trips, the computer tells me I get between 8.5 and 9(.5). My engine is only a 6.7l which I have been told gets better mileage than the larger block.

[kevin]

The only long trip I have made showed me 10 mpg on the engine computer. That was driving all day on the interstate. When I go on shorter trips, the computer tells me I get between 8.5 and 9(.5). My engine is only a 6.7l which I have been told gets better mileage than the larger block.

Do you ever just check it with the milage, gals put back into the MH? our computer showed that we were getting 8 once, and it was really about 6, then it showed 4 once or twice, and it was really about 6.5.

[RV Roamer]

The computer mpg readouts are notoriously optimistic, but usually only  a few (or several) tenths rather than 1-2 mpg. Manually calculating mpg by tracking gallons purchased vs miles actually driven over several thousand miles is the only way to get areal handle on your mileage.

The Cummins ISB (5.9L or now 6.7L) is quite fuel efficient, but it is also used in lighter or shorter RVs and that helps too. The Cat 3126 is another miserly engine.  Not surprisingly, it takes more fuel to feed the 8.3 and 8.9L big block engines that are driving the 34k-40k lb 40-45 footers.

Fuel economy also took a downward step when the new EPA regs for diesels went into effect on 1/1/2007.

[kevin]

Roamer, If just excepted the fact that I get...at best 6.8, at worst...4.4 and usually I end up getting 6.5 I've tried the 65mph thing, I've tried the 70mph, and 75, but I just can't seem to get the 8mpg or the even the 7mpg that I hear about So as long as  I know that going into this, I'm ok with it..well sort of

Ps love the new faces