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Author Topic: Diagnosing Poor MPG  (Read 1832 times)

Heli_av8tor

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Diagnosing Poor MPG
« on: August 29, 2017, 09:24:58 AM »
I've been following this thread (and other similar) with interest.
My coach is getting between 5 and 5-1/2 mpg. I'm thinking based on others that this is at least 20% low. My cruise speed has varied from 55 to 68 with most around 60.
The coach weighs about 22,500 loaded and the toad is 3400. There is 48,000 miles on the coach.
I don't try to accelerate like a race car and anticipate stops and speed reductions so as to keep braking to a minimum.

Assuming it should do better, what should I look for? Does any of the OBD info give a clue?

Tom
Tom & Theresa
2004 Pace Arrow 37C
Workhorse W22, 8.1 Vortec
2014 Honda CR-V Toad, Roadmaster -5 Base and tow bar
SMI Stay and Play Duo Brake system

Charlie 5320

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Re: Diagnosing Poor MPG
« Reply #1 on: August 29, 2017, 10:59:12 AM »
I've been following this thread (and other similar) with interest.
My coach is getting between 5 and 5-1/2 mpg. I'm thinking based on others that this is at least 20% low. My cruise speed has varied from 55 to 68 with most around 60.
The coach weighs about 22,500 loaded and the toad is 3400. There is 48,000 miles on the coach.
I don't try to accelerate like a race car and anticipate stops and speed reductions so as to keep braking to a minimum.

Assuming it should do better, what should I look for? Does any of the OBD info give a clue?

Tom
Air filter, clean the maf sensor, and have it scanned to see if the 02 sensors are switching. They should switch very quickly, if they switch but are slow to react, may be a cause of a rich condition. My 8.1 doesn't get the fuel economy my old 7.4s did, but it's got a LOT more power. On my last 1200 mile trip my 19600 lb coach got 7.5 to 7.6 mpg running the speed limit most of the time. 36000 miles on the coach with original plugs and wires, it does have a K&N air filter the PO owner installed. I'm going to replace it with a Wix filter before the next trip to see if either one makes a difference.
2003 National Dolphin 5320
496  8.1  Workhorse

98 Damon Daybreak 3130
GM Vortech 454  4L80E
SOLD

Heli_av8tor

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Re: Diagnosing Poor MPG
« Reply #2 on: August 29, 2017, 12:17:33 PM »
The air filter is new.
I have not cleaned the MAF sensor.
I'm not sure what you mean by the O2 sensors not switching quickly.
The engine is operating in "closed loop". And the short term fuel trims are very responsive with any changes in load or throttle. Both banks are virtually identical in values and response.

Tom
Tom & Theresa
2004 Pace Arrow 37C
Workhorse W22, 8.1 Vortec
2014 Honda CR-V Toad, Roadmaster -5 Base and tow bar
SMI Stay and Play Duo Brake system

kdbgoat

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Re: Diagnosing Poor MPG
« Reply #3 on: August 29, 2017, 12:28:28 PM »
O2 sensors operate at a high frequency. If the frequency is too low, it will cause the system to operate incorrectly. It used to be a common problem at some shops as they would check them with an ohm meter to be either open or closed, instead of using a proper scanner to check the frequency. Sometimes it was the scanners fault as that is all the scanners would read. 
I know you believe you understand what you think I said,
But I am not sure you realize what you heard is not what I meant


2016 Leprechaun 319DS

SeilerBird

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Re: Diagnosing Poor MPG
« Reply #4 on: August 29, 2017, 12:29:09 PM »
I've been following this thread (and other similar) with interest.
My coach is getting between 5 and 5-1/2 mpg. I'm thinking based on others that this is at least 20% low. My cruise speed has varied from 55 to 68 with most around 60.
The coach weighs about 22,500 loaded and the toad is 3400. There is 48,000 miles on the coach.
I don't try to accelerate like a race car and anticipate stops and speed reductions so as to keep braking to a minimum.

Assuming it should do better, what should I look for? Does any of the OBD info give a clue?

Tom
You really should start a new thread to get some answers. This thread is almost dead.
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Charlie 5320

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Re: Diagnosing Poor MPG
« Reply #5 on: August 29, 2017, 03:51:50 PM »
The air filter is new.
I have not cleaned the MAF sensor.
I'm not sure what you mean by the O2 sensors not switching quickly.
The engine is operating in "closed loop". And the short term fuel trims are very responsive with any changes in load or throttle. Both banks are virtually identical in values and response.

Tom
A good 02 sensor will move around with no input from the throttle. With my Mac scanner I can see the voltage change constantly with no throttle movement. Cheaper scanners may not show this, I don't know. I had a 7.4 a few years ago that would occasionally have a check engine light, caused by a lazy 02 sensor. Fuel mileage picked up after it was changed, but it didn't appear to be fouled like most are, when they trigger the light.
2003 National Dolphin 5320
496  8.1  Workhorse

98 Damon Daybreak 3130
GM Vortech 454  4L80E
SOLD

Heli_av8tor

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Re: Diagnosing Poor MPG
« Reply #6 on: August 29, 2017, 09:19:45 PM »
You are right, it should be a new thread and I've done that.

See "Diagnosing Poor MPG"

Thanks to all for your thoughts. Please continue in the new thread.

Tom
Tom & Theresa
2004 Pace Arrow 37C
Workhorse W22, 8.1 Vortec
2014 Honda CR-V Toad, Roadmaster -5 Base and tow bar
SMI Stay and Play Duo Brake system

Heli_av8tor

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Re: Diagnosing Poor MPG
« Reply #7 on: August 29, 2017, 09:23:24 PM »
I started this question in another thread and decided it should be its own topic.

My coach is getting between 5 and 5-1/2 mpg. I'm thinking based on others that this is at least 20% low. My cruise speed has varied from 55 to 68 with most around 60.
The coach weighs about 22,500 loaded and the toad is 3400. There is 48,000 miles on the coach.
I don't try to accelerate like a race car and I anticipate stops and speed reductions so as to keep braking to a minimum.

Assuming it should do better, what should I look for? Does any of the OBD info give a clue?

Tom
Tom & Theresa
2004 Pace Arrow 37C
Workhorse W22, 8.1 Vortec
2014 Honda CR-V Toad, Roadmaster -5 Base and tow bar
SMI Stay and Play Duo Brake system

Tom

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Re: Diagnosing Poor MPG
« Reply #8 on: August 29, 2017, 09:58:01 PM »
Quote
I started this question in another thread and decided it should be its own topic

I merged the two topics so all the replies are in one place, rather than having two parallel topics.
Tom.  Need help? Click the Help button in the toolbar above.

WILDEBILL308

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Re: Diagnosing Poor MPG
« Reply #9 on: August 29, 2017, 10:03:10 PM »
I started this question in another thread and decided it should be its own topic.

My coach is getting between 5 and 5-1/2 mpg. I'm thinking based on others that this is at least 20% low. My cruise speed has varied from 55 to 68 with most around 60.
The coach weighs about 22,500 loaded and the toad is 3400. There is 48,000 miles on the coach.
I don't try to accelerate like a race car and I anticipate stops and speed reductions so as to keep braking to a minimum.

Assuming it should do better, what should I look for? Does any of the OBD info give a clue?

Tom
Tom, With the weight you are pulling that isn't that bad. I think there are some things you could try. It depends on how much work you can do yourself. Do you have a stock exhaust? What have you tried sofar?
Bill
2003 Bounder 38N
300 HP 5.9 Cummins
Allison 3000MH Trans.
Towing 2014 Honda CRV
Home base Fort Worth, Texas
A man who carries a cat by the tail learns something he can learn in no other way.
-Mark Twain-

Heli_av8tor

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Re: Diagnosing Poor MPG
« Reply #10 on: August 29, 2017, 10:41:41 PM »
Thank you Tom.

My Exhaust is stock: Dual 3" through CC and Muffler. Then Y-pipe to single 4" tailpipe.

To clarify, the Short Term Fuel Trim is constantly and rapidly changing.

I'm using a WIFI OBD to my iPad for a scanner.

I've been so busy with other repairs that I haven't tried anything other than looking at the data from the OBD and trying to spot something there. And trying to figure out what to try.

I realize the 5.0 to 5.5 is not totally in the toilet, but it does seem 20% lower than others are "claiming".

Tom

Oh, my new tailpipe is clean after a 120 mile trip.
Tom & Theresa
2004 Pace Arrow 37C
Workhorse W22, 8.1 Vortec
2014 Honda CR-V Toad, Roadmaster -5 Base and tow bar
SMI Stay and Play Duo Brake system

Arch Hoagland

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Re: Diagnosing Poor MPG
« Reply #11 on: August 30, 2017, 12:09:01 AM »
I get 7.1 averaged over 87,000 miles, hand calculated. I weigh in at about 26,000 lb with the toad so you are low.

My speeds are similar to yours.

How are you calculating you gas mileage...by hand or by readout?

Over how many miles is your mpg calculated?  It can vary trip by trip depending on where you go. wind, terrain, etc.

You really need to clean your MAF as it helps determine the fuel to air mixture.

Have you replaced your plugs and wires?
2004 Monaco La Palma 36 DBD
W22, 8.1 gas,  Allison 1000 Transmission
7.1 MPG over 80,000 miles

2000 Lexus RX300, 4020lb
U.S. Gear Braking System

Bill N

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Re: Diagnosing Poor MPG
« Reply #12 on: August 30, 2017, 06:51:45 AM »
Don't forget to consider how much the generator is used.  On very hot days and with 3 animals in the coach (and two humans) we do run the generator on the highway to keep the whole coach cool and that would affect your overall gas mileage as the gen is dipping out of the same tank.  Just a thought.

Bill
Bill & Joan N in Missouri
USAF (Ret)
2002 Winnebago Adventurer 35U
Workhorse W22, 8.1L Chevy V8
2013 Chevy Sonic Toad
Furbearers:  Heidi-17(Forever), Grace-10 & Squeak-4, Winnie - 8 months

boatbuilder

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Re: Diagnosing Poor MPG
« Reply #13 on: August 30, 2017, 07:17:41 AM »
O2 sensors will rarely cause the check engine light to come on.  Many times it is easier to just change them than spend the time to try and diagnose them.  I know many mechanics just change them every time they change spark plugs just as a preventative measure.
Charlie

Heli_av8tor

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Re: Diagnosing Poor MPG
« Reply #14 on: August 30, 2017, 07:54:13 AM »
I calculate MPG the old fashion way, well, I do use a handheld calculator lol. My mileage was calculated over a 1800 mile trip (East from Iowa, across Illinois, into Indiana, to UP of Michigan, south through Wisconsin, back to Indiana, then to Iowa. The generator was used about 8 hours tops on this trip so would account for maybe 0.1 mpg. Engine A/C was run continuously. We did experience some mean cross-winds, but seldom had much headwind component to them.

I've not changed plugs or wires. Should it need plugs at 48,000?

I'm reluctant to just start throwing money at possible causes but it may come down to that.

I have a trip to Colorado in less than two weeks and may not have time to do much before we leave.

Thanks,
Tom
Tom & Theresa
2004 Pace Arrow 37C
Workhorse W22, 8.1 Vortec
2014 Honda CR-V Toad, Roadmaster -5 Base and tow bar
SMI Stay and Play Duo Brake system

Heli_av8tor

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Re: Diagnosing Poor MPG
« Reply #15 on: August 30, 2017, 09:14:23 AM »
I'm starting to price O2 sensors and seeing a range from the $80's to over $200.
Any suggestions?
Tom & Theresa
2004 Pace Arrow 37C
Workhorse W22, 8.1 Vortec
2014 Honda CR-V Toad, Roadmaster -5 Base and tow bar
SMI Stay and Play Duo Brake system

Gary RV_Wizard

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Re: Diagnosing Poor MPG
« Reply #16 on: August 30, 2017, 09:43:33 AM »
I would say the 5.0-5.5 mpg IS indeed "totally in the toilet" if that is highway mileage. That rig should easily get 7 mpg, even with a heavy foot. The one we had was a hair under 22,000 lbs, plus a 3500 lb toad, and we averaged 7.6-8.1 mpg over 50k miles.

I'm inclined to be skeptical about lazy O2 sensors, but it's conceivable I guess. Generally, though, if the sensor is working well enough for the ECM to get into closed loop mode, it should be ok.  But I confess I don't see how it could be operating closed loop and get such poor mileage unless the engine is always running near WOT, i.e under heavy load.  Is the tranny getting into OD?  No brake drag or anything like that? What are you seeing for engine rpms when cruising at highway speeds?   I think your '04 has only the 5-speed Allison, right?

I seem to recall the 8.1L has two O2 sensors, one in each bank? Can anyone verify or disprove that?
« Last Edit: August 30, 2017, 09:45:28 AM by Gary RV_Wizard »
Gary
--------------
Gary Brinck
Summers: Black Mountain, NC
Home: Ocala National Forest, FL

boatbuilder

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Re: Diagnosing Poor MPG
« Reply #17 on: August 30, 2017, 09:59:26 AM »
Just due to age, I would pull out a couple spark plugs and see what they look like.  It would probably be worth it just to change at least the plugs and the maybe O2 sensors.
Charlie

Heli_av8tor

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Re: Diagnosing Poor MPG
« Reply #18 on: August 30, 2017, 12:07:12 PM »
It has an O2 sensor on each side in front of the CC. both banks report very similar fuel trims and seem to be constantly changing. I too really have trouble thinking they are at fault. It is definitely in closed loop.

It has the Allison 5-speed and gets to OD around 55 to 60 depending on load. RPM's around 2200 at 60 (from memory).

I'm not positive that the brakes are not dragging, but I have seen no indications. Will look more closely at that possibility on my next drive. The calipers were replaced just before I got the coach.

Tom
Tom & Theresa
2004 Pace Arrow 37C
Workhorse W22, 8.1 Vortec
2014 Honda CR-V Toad, Roadmaster -5 Base and tow bar
SMI Stay and Play Duo Brake system

Gary RV_Wizard

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Re: Diagnosing Poor MPG
« Reply #19 on: August 30, 2017, 08:39:44 PM »
It's conceivable one or more plugs are fouled at 48k, but usually they are good for 100k or better. Worth a check, though, because the condition of the plug is a good barometer of how well the air/fuel mixture is being controlled.

You seem to already have a good understanding of how the closed loop ECM system works, so I'm not sure we can help a lot more without getting in there beside you with meters and visual inspections..
Gary
--------------
Gary Brinck
Summers: Black Mountain, NC
Home: Ocala National Forest, FL

Heli_av8tor

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Re: Diagnosing Poor MPG
« Reply #20 on: August 30, 2017, 09:20:12 PM »
Just finished replacing the exhaust Y pipe so can now devote my efforts to the mpg problem.

Tomorrow I'll start with cleaning the MAF sensor and verifying that the dealer actually replaced the air filter as claimed.

I'll also pull and inspect the plugs.

Will report my findings.

Tom
Tom & Theresa
2004 Pace Arrow 37C
Workhorse W22, 8.1 Vortec
2014 Honda CR-V Toad, Roadmaster -5 Base and tow bar
SMI Stay and Play Duo Brake system

Arch Hoagland

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  • Clovis CA
Re: Diagnosing Poor MPG
« Reply #21 on: August 30, 2017, 09:54:17 PM »
"Just finished replacing the exhaust Y pipe so can now devote my efforts to the mpg problem. "

My 2004 W22 has dual exhausts not tied together. Did you go to dual exhaust or just put in a new Y pipe? 

Dual exhausts will help with power and MPG. 

I'll respectfully disagree with Gary about the plugs on a GM going 100,000 miles. Mine have been replaced twice in 87,000 miles as well as the wires.
2004 Monaco La Palma 36 DBD
W22, 8.1 gas,  Allison 1000 Transmission
7.1 MPG over 80,000 miles

2000 Lexus RX300, 4020lb
U.S. Gear Braking System

Heli_av8tor

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Re: Diagnosing Poor MPG
« Reply #22 on: August 31, 2017, 06:46:24 AM »
I replaced the Y pipe. The inlet of this pipe is two 3" converging into a 4" outlet.
May have been better to have kept them separate but I didn't do that.

Back in my motorcycle racing days we would test spark plugs by tossing them into the air. If they stayed up there they were good. If they come down - replace them. I'll apply the same test on the MH plugs.
If I can get my compression tester in I'll check while the plugs are out.
Tom & Theresa
2004 Pace Arrow 37C
Workhorse W22, 8.1 Vortec
2014 Honda CR-V Toad, Roadmaster -5 Base and tow bar
SMI Stay and Play Duo Brake system

Gary RV_Wizard

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Re: Diagnosing Poor MPG
« Reply #23 on: August 31, 2017, 09:24:49 AM »
Quote
I'll respectfully disagree with Gary about the plugs on a GM going 100,000 miles. Mine have been replaced twice in 87,000 miles as well as the wires.

LOL! No need to be "respectful" about something that is largely a matter of opinion!  ;)

I'll stand by my previous comments, though. If the ECM is managing the closed loop system as it is designed to do, the plugs should last 100k miles.  If the air/fuel mixture is maintained at the proper stoichiometric value, the plug should show no signs of damage or wear.  No fouling or burning evident and not even much physical electrode loss. I'll grant, though, that plugs will show more deterioration in an engine that does mostly stop and go driving, or rarely run long enough to get up to full operating temperature. The fuel mix gets somewhat rich during accelerations or deceleration and that hastens plug wear.
Gary
--------------
Gary Brinck
Summers: Black Mountain, NC
Home: Ocala National Forest, FL

Heli_av8tor

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Re: Diagnosing Poor MPG
« Reply #24 on: August 31, 2017, 07:56:34 PM »
I cleaned the MAF sensor today. There was no visible contamination. The air cleaner was not new as claimed by the selling dealer. The paper part looked very good. However, the foam pre-filter (that fit over the paper like a bonnet) had some blockage (10%?). I tried washing it with soap and water and it started crumbling. A replacement will be here Saturday.

I also ordered plugs and wires. Amazon had a great deal on ACDelco 41-101 Professional Iridium Spark Plugs. Best I can research this should be a good plug for this engine. I didn't pull any plug wires as they didn't act like they were going to release and I needed to drive it to my storage lot.

Wires, plugs, and filter should be here Saturday. I'm still on the fence with the O2 sensors...

Tom
Tom & Theresa
2004 Pace Arrow 37C
Workhorse W22, 8.1 Vortec
2014 Honda CR-V Toad, Roadmaster -5 Base and tow bar
SMI Stay and Play Duo Brake system

WILDEBILL308

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Re: Diagnosing Poor MPG
« Reply #25 on: August 31, 2017, 09:19:36 PM »
It has an O2 sensor on each side in front of the CC. both banks report very similar fuel trims and seem to be constantly changing. I too really have trouble thinking they are at fault. It is definitely in closed loop.

It has the Allison 5-speed and gets to OD around 55 to 60 depending on load. RPM's around 2200 at 60 (from memory).

I'm not positive that the brakes are not dragging, but I have seen no indications. Will look more closely at that possibility on my next drive. The calipers were replaced just before I got the coach.

Tom
There are a number of small things that might help your milage. Simple things like using a full synthetic oil like Mobil 1, Free flowing exhaust. Yes I would jack it and see if the wheels spin without undue drage. One big thing DO NOT use a K&N type filter as they let to much dust to get past.
Are the tires the correct size as specked for your coach? there should be a data plate.
I picked up a 6.6% increase in GPS speed over what the speedometer shows. Have you checked what your actual/GPS speed is?
You might look at one of the aftermarket tuners like Bully Dog, https://www.bullydog.com/
or Banks, http://shop.bankspower.com/
Lots to look at and research.
Tried to post this yesterday but found it haden't.
Bill
« Last Edit: August 31, 2017, 09:24:20 PM by WILDEBILL308 »
2003 Bounder 38N
300 HP 5.9 Cummins
Allison 3000MH Trans.
Towing 2014 Honda CRV
Home base Fort Worth, Texas
A man who carries a cat by the tail learns something he can learn in no other way.
-Mark Twain-

rls7201

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Re: Diagnosing Poor MPG
« Reply #26 on: September 01, 2017, 07:21:18 PM »
 On Oemy's Workhorse web site is a list of O2 sensors that will work on your coach. Lots of good Workhorse stuff there.
http://www.oemys-performance.com/whparts.htm

W8000524       O2 Sensor   OEM
12572706       O2Sensor   AC Delco/RockAuto
213-1161      O2 Sensor   AC Delco
15282       O2 Sensor   Bosch
5S4403      O2 Sensor   Airtex/Wells
234-4669      O2 Sensor   Denso
21549      O2 Sensor   NGK
250-24491   O2 Sensor   Walker
Richard  & Michele Shields
& Eg the Bounder Cat
Gladstone, MO
95 Bounder 32H F53
460/528 stroker

DearMissMermaid

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Re: Diagnosing Poor MPG
« Reply #27 on: September 01, 2017, 09:44:44 PM »
Gas records.

Are you keeping accurate gas records?

Since I bought my rig, I have logged in every gas purchase and the odometer readings. I always mark my purchase with whether or not I filled the tank full. That way I can go back and calculate the actual gas mileage. I transferred the log to  an ongoing spreadsheet and worked out the costs and miles per gallon.

Most folks when estimating their miles per gallon,  just get it plain wrong. You really need to keep detailed ongoing records to get an accurate picture. In my log book I also mark down everywhere I have spent the night. So the entire time I've owned my rig, I know where I went, where I camped.

That information has been fun and very helpful, as I sometimes do repeat visits and similar trips to get back to places I enjoyed so much, I wanted to go back again.

Now in my case, I started out keeping up with generator use and gave up on that, too much work. So, my gas mileage does vary because the generator drains off the same tank. So that throws a monkey wrench in the works. I have an hour meter on my generator, but I am not convinced it works correctly.

So the summers I workamped, my miles per gallon was much higher than the summers I traveled. This is because when I travel in the summer, I sometimes have to use the generator on hot humid days in addition to the dash AC. When I was workamping all summer, I only used the generator once or twice a month to exercise it.

Driving around mountains made my miles per gallon go down, driving around flat Florida, my miles per gallon goes up again.

Sometimes the gas mileage went haywire during an emergency. For instance I had emergency surgery while my RV and dog were parked in the hospital lot running the generator nonstop. Then it was 5 miles to the campground. So 24 hours of generator plus 5 miles driving reduced the 55 gallon tank  about a fourth which is about 13 gallons. Noting that in my log book helps me remember when I get around to compiling my spreadsheet.

It would be easy to think something was bad wrong that between those fuel fills I got such dismal miles per  gallon, but I was careening around medical facilities with the generator running full tilt boogie.

Headwinds and tailwinds can affect gas mileage too as well as whether you are towing or not towing.

To budget for trips I figure a worst case scenario with only 6 miles per gallon and factor in  the highest cost per gallon for gas purchases. That way I always come in under budget on the trip (for gas) when all is said and done.  (Except for the trip that landed me in medical hell.)

I generally get about 8.5 miles per gallon AVERAGE in my Class C including the generator usage (that is after compiling several years of keeping records)  and I often do travel with full water tank and full gas tank. I don't like to let my gas get below a half tank. If an emergency comes up, I want gas for the generator. The only time my rig has needed road side assistance was on overly hot humid days, so having that gas available to fire up the generator was life saving.

If you don't have good accurate ongoing records, then it's possible you don't have a problem at all.

By the time you factor in generator, towing, winds, mountains and so on. 5.5 mpg may be about right for your rig.
http://DearMissMermaid.Com

Living, working. playing  in a Class C, 1994 Tioga Montara, 28'

Pack half the stuff and twice the cash.
http://dearmissmermaid.blogspot.com/

Heli_av8tor

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Re: Diagnosing Poor MPG
« Reply #28 on: September 04, 2017, 10:01:16 AM »
OK, first to answer some of the questions posed.
The GPS speed matches the dash speedo. I have not checked it against the odometer.
Thanks for the Oemy's reference. It has been a help.
The tires are new Michelin's and are the correct size. (MICHELIN XRV 235/80R-22.5)
I too keep detailed logs including generator use.

When I cleaned the MAF sensor I found some corrosion on one terminal of the 4 pin connector. I cleaned both plug and socket and applied a thin coating of DeOxIt.
I'm hoping this is the "smoking gun".

I found the plugs to be the light to medium tan color. A couple had more buildup on the ground electrode where it meets the plug body than others. Not terrible but as cheap as they have become I'm glad I replaced them.
Some of the plug wires were impossible to get off without damage. Many of the plug boots under the metal shield were dried out and brittle. A new set is installed.
Based on the plug inspection I decided not to do a compression check as I didn't know if cranking without plugs and starting would throw any codes.

I did a 30 mile test drive last night. The up and down shifting seemed more appropriate (like I would do if a manual tranny) than before. The engine just seemed overall smoother. The rolling average mpg on the trip computer went from 5.1 to 7.1 mpg. some indication that it may be getting better mpg but not definitive. The test route had less residential than before and the wind was fairly calm.

Looks like we will be taking our Colorado trip without replacing the O2 sensors. This trip will tell me if I've made any real improvement. Will report results.

Thanks to all who helped me.

Tom
Tom & Theresa
2004 Pace Arrow 37C
Workhorse W22, 8.1 Vortec
2014 Honda CR-V Toad, Roadmaster -5 Base and tow bar
SMI Stay and Play Duo Brake system

Gary RV_Wizard

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Re: Diagnosing Poor MPG
« Reply #29 on: September 04, 2017, 10:09:55 AM »
Incorrect readings from the MAF sensor will certainly cause the ECM to miscalculate, so that corrosion could indeed be a "smoking gun". The engine constantly runs rich (or lean) if the MAF values are inaccurate.  Hope that solves the mpg problem for you.

I just read an article that says a common source of inaccurate MAF readings is from an over-oiled aftermarket air filter. Maybe that K&N filter was the root cause? 

https://www.yourmechanic.com/article/symptoms-of-a-bad-or-failing-mass-airflow-sensor
« Last Edit: September 04, 2017, 10:13:08 AM by Gary RV_Wizard »
Gary
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Gary Brinck
Summers: Black Mountain, NC
Home: Ocala National Forest, FL

 

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