4.9 MPG ??? wow

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93Coachman

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Jun 22, 2014
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OK just got in from third trip  we have been doing several short trips to local campgrounds to get the bugs out of the old bus.  Started a few weekends ago with a full tank of fuel  mostly two lane road KY roads where they threw down a snake an followed it with a paver ;D    filled up this afternoon and checked mileage.  Wow a wopping 4.9 MPG.  We have a 93 coachman Chevy 454  400 tranny.  Regular fuel shell mostly.  Where do I start to see if I can improve this mileage ??  Surely it should do better then this. Thanks. DON
 
Start with the usual things for any motor vehicle. Tune up...plugs and air filter, and tire pressure.
Next...how fast were you driving? These "bricks" don't do very well above about 55 mph.

I have a 2002 Minnie 22' and get between 7.5 and 9...as long as I keep my foot out of it. If I run down the freeway at 65, mileage drops to between 6.5 and 8.
(I would expect yours to get better than 4.9...just not a LOT better)
 
Aside from the mechanical items already mentioned, probably the single biggest fuel waster is one's foot.  Quick starts with "pedal to the metal" and higher speeds will kill your MPG.  Based on your description of Kentucky's two-lane roads I would guess that you might be trying to keep up to speed so you don't hold up traffic.  If so, you'll be pushing the gas pedal a lot.  Slow down and pull over if there's a long line of cars trying to pass and then start back up as gently as possible.  Check your fuel again after another trip of easing off the gas pedal and see if there's a change.  By the way, going up mountains with cruise control on also will kill MPG because the engine is working really hard to maintain the set speed.

ArdraF
 
Thanks.  Air filter looks like new,  don't see any leaks from fuel,  tire pressure yep could be a problem gonna check today,  and will pull a plug or two today 

I've been trying very hard to do the 58 thing  its taking time to hold back. That is not easy this thing wants to fly with that big motor
What about the exhaust system would dual exhaust and flowmaster's    do anything but make it sound great ?   





 
93Coachman said:
I've been trying very hard to do the 58 thing  its taking time to hold back. That is not easy this thing wants to fly with that big motor
Click to expand...
I have a 1994 class A with a 454 and I set the cruise control at 55 and never have a problem.
 
Headwinds can drop your mileage quickly, too. You need to check it over a longer time than one or two tankfuls. Of course running the generator or driving in a lot of city traffic (especially stop and go) can cut your mileage, also.
 
We have a 93 coachman Chevy 454  400 tranny.  Regular fuel shell mostly.  Where do I start to see if I can improve this mileage ??  Surely it should do better then this.
Click to expand...

Maybe a bit, but not much. The engine is a fuel hog, the tranny only a 3-speed, and that big coach forces both to work at near-max all the time. Your goal might be only 6 mpg. A couple years newer and it might see 7.5, but the early 90's weren't kind to big gas motorhomes. Plus you were in a worse case scenario for motorhome mpg, driving twisty two lane roads on short trips.  The frequent acell/decell is an mpg killer.  Your best mileage will be cruising an interstate at about 55 or so.  You also can't judge much based on one tankful - too many variables to be sure. If you filled it an extra gallon or two more than the previous "full", your mpg gets distorted a fair amount.

An improved exhaust would probably help some, but you would need headers and everything, so probably cost more than you could ever save in fuel. A lot more.
 
Hard to determine mileage with one tank.  If we were on an extended trip and averaged 4.9 mpg our motorhome would be up for sale. 

We bought our motorhome 4 months ago.  It is a Ford V10 and has the 3 speed with overdrive tranny.  This is our first trip and we've been on the road for about 2 months.  I try to keep it under 60 but the old V10 can easily move it along at 70.  Have driven close to 4,500 miles and will add another 2,000 before we're home.  I keep a mileage log and the average mpg over 4,066 miles is 7.2.  The range is from 4.3 and 8.325.  However, we have also run the generator continuously.  In total, we have used the generator for 100 hours.  I'm not sure how much fuel the gene takes but if it's 1/2 gallon per hour, the average increases to 7.94. 

The 4.3 mpg occurred when we refilled the tank after only 30 miles.  That was likely because the previous tank was not topped off.  I've noticed that we can drive from 25 to 50 miles after a fill before the needle drops below the full mark.  To me, that indicates a tank that was from 1 to 3+ gallons from full. 
 
Thanks for all the talk. I'll relax and just watch my driving habits.  I have to remember I'm retired and in do hurry driving in the left lane with my blinker on  8)  the old bus is for sure going on a 1000 mile run to be my winter home now weather it comes back or not wait and see.  Its up to him and his mileage if he comes home or not  you guys make me feel better
 
I have a gas-engine Class C, 22ft, which is much smaller and lighter obviously.  Just to speak to the "slow down" idea:

My gas mileage just tanks if I go too much faster than 55MPH.  I can manage >10MPG at 63MPH on the highway.  I'm not retired, so stealing away from work days on my trips, and I have to fight the "need" to drive faster.  We make time up not stopping for bathroom breaks, or cooking, or eating, or while our kids sleep (still buckled in of course).

Our rig is small enough that I can cool the entire thing from the dash (vehicle's) A/C, so I save some on the generator.  You might find your generator's manual talks about fuel use: my little 4kW burns 0.5gal/hour at an idle 1.5gal/hour at full use (i.e. microwave or rooftop A/C). 

I installed a small inverter that runs off the vehicle alternator, because when we're driving long days, we're charging multiple cameras, phones, tablets, ipods/ipads etc. about 10 hours a day, but only use the generator when using the microwave or big TV.  I'd hate to run the generator all day long just use a few amps to charge minor hand-held devices.
 
I had a 26' C with a 460 in it and found that as said above, my biggest enemy was my heavy foot. Fast starts, pedal to the floor up hills,etc I would be lucky to get 5mpg.

If I made slow starts, and generally took it easy I could often squeeze 8 or 9 mpg out of it. Always tried to keep it under 60 on the highway also.
 
My old class C 29' would do 8 mpg consistantly as long as I kept my foot out of it, but man the horses in that 460 wanted to get up and went.  If I was real attentive I might squeeze 9 mpg, but that was rare.  Now my 38' A DP is a different kettle of fish I get 10 mpg consistantly and that is with a toad on a dolly.  Of course I am rarely over 60 mph with it.  I don't worry to much about going, I worry about stopping. 
 
Just as an item of interest here; increasing your speed from 55 to 70 mph approximately doubles the drag. On reasonably flat roads, I'd guess the drag is responsible for 60% of the overall power required to maintain speed. Note that a 15 mph headwind will have the same effect! 

Incidentally, force of impact also doubles for the same speed increase. Both are a function of velocity squared.

Ernie
 
you have a 4 barl carb that is stuck open some

the last 2 barls  after age like to stick open some  and if you have a small amount of high idle  this is why

take your finger and push on the leaver  that is used to open it the spring well push it back  oil and play with this  in tell you feel its closed all the way

sorry for spelling errs
 
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