Expected fuel mileage for a Diesel Motorhome

[Mike Thomas]

Every diesel has a sweet spot, where torque and performance is maximized. Manufacturers have that information on their websites. The last semi tractor I owned it was 1825 rpm. If I drove at that rpm everything was maxed out.

The general rule of thumb is for every 1 mph over the sweet spot, you lose .1 mpg So if 62 mph is the sweet spot, at 72 mph you would lose .1 x 10 equals 1 mpg. It will generally work that way.

I have a 1999 American Eagle and pull an 20 foot enclosed trailer with a Model T in it. I drove from Iowa to Albuqurque with a 35 mph head wind all the way. Averaged 6.5 mpg. Coming back I had the same wind, only it was a tail wind and averaged 9 mpg. Generally I figure 7 to 7.5. Cummins ISC 350 horse power.

[Fiesta48]

05 V10 9.0 mpg, 11 V10 8.0 mpg (heavier, no car), 15 ISL diesel 8.9L 9.0 mpg (50% heavier, & pulling a car), but much more relaxed. Retired, I drive sanely, why rush?

[VestaDave]

Originally Posted by RickyM

My wife and I just recently bought a new 2016 fleetwood pace arrow 38 ft with 340hp 6.7L isb cummins motor. We just got back from a 2 wèek trip to NH and ME. Over 1000 miles there and back towing a jeep Cherokee. We averaged 9 mpg with average speed of 65 mph . I really expected better fuel economy, with all the new requirements on emissions. I understand it's a big square box on 6 wheels but with all the technology out there it seems that these engines should get better fuel economy.

Don't get me wrong I absolutely love our new motorhome but I would like to get better fuel mileage then 9 mpg.

I'm going to guess that this comment is "tongue in cheek". Judging by all the other entries here 9 mpg is not only good , it's awesome!! Given your ave. speed, weight and tow you should be less mpg.

[Crasher]

When we travel from WI to AZ in the fall, I stop twice for fuel. If I had a gas coach, I would have to stop four times and make two trips to get everything there, so I guess the diesel gets better milage.

[TBS-POPS]

8 with a head wind, 12 with a tail wind . Usually fall in the 9-10 range. ISC 330.

[Rich-n-Linda]

Originally Posted by RickyM

...Don't get me wrong I absolutely love our new motorhome but I would like to get better fuel mileage then 9 mpg.

LOL!! Dream on...it will never get any better than that.

At 9 mpg you are already slightly above average.

[Steve Ownby]

Originally Posted by RickyM

My wife and I just recently bought a new 2016 fleetwood pace arrow 38 ft with 340hp 6.7L isb cummins motor. We just got back from a 2 wèek trip to NH and ME. Over 1000 miles there and back towing a jeep Cherokee. We averaged 9 mpg with average speed of 65 mph . I really expected better fuel economy, with all the new requirements on emissions. I understand it's a big square box on 6 wheels but with all the technology out there it seems that these engines should get better fuel economy.

Don't get me wrong I absolutely love our new motorhome but I would like to get better fuel mileage then 9 mpg.

The emissions requirements are a story of diminishing returns. The computer controls that run Diesel engines now are so precise that I'm guessing all the emissions specific hardware could be removed and they would still be pretty clean. The hardware required to meet emissions standards do nothing to enhance economy. The worst system for economy is the EGR system which was the first requirement. The addition of the DEF system on 2010 and later engines actually resulted in some economy and power gains because the EGR could be de tuned somewhat. Your ISB engine has long been an economy champ in motorhome service. 9 mpg is pretty good. If you are willing to slow down to 60, you will pick up some more mileage.

[Scottybdivin]

6.5 average for my Cummins ISM 450 towing the F150 65 MPH. Total weight is about 49K.

[Spizzer]

We run a 34ft with a Cat C7 towing a Jeep Grand Cherokee. If I drive 62-63 mph I get around 8.7 mpg. Fighting winds I'll get 7.5. Interestingly, when we were driving across the causeway in Louisiana, it is flat, and there was no wind. I set the cruise on 55 mph and the computer settled in on 10mpg. Bumped it up to 60 mph and it was 9 mpg. 65 mph gave me 8 mpg, and you guessed it, 70 mph was 7 mpg.

As a side note, driving 62 mph I find myself much more relaxed than even 65. Driving is a pleasure, and I'm not exhausted at the end of the day.

Jeff

[dubbyjig]

Our most recent trip we got 9.7 mpg
ISB 275 hp

Around 33,000 lbs

Try to keep it at 65 mph