Diesel Motorhome MPG-- Honest Answers Please

[slemnah]

My 525hp CAT C13 is a very thirsty kitty. I weigh 42k lbs and the average fuel economy is 5.4mpg. I have tried numerous things to increase it but at the end of the trip I am around that number. It doesn't seem to matter if I am towing my Ford Edge or not. I just purchased the trailer and will be making my first trip soon so I will see if the mileage drops. I will say that I love the way that it drives and pulls the hills and I usually stay around 62-65 mph.

[billbaldwin]

I have a 2012 Winnebago Journey 42E w/Tag

400hp Cummins

I just returned from a 1,500mi trip

No toad but motorcycle on back (Hydrolift)

9.5 mpg

[BennieH]

Just finished our maiden trip with the new to us 2003 40' Monaco Camelot, 350hp Cummins towing our Saturn Aura and the total average was 9.1 mpg. we tried to run at 1600rpm (peak torque) which was 63 mph.

I am very pleased with that since our 31' "C" Ford V10 did about 7.2mpg.

[tbutler]

I don't know what fuel mileage I get going up hill, every hill is different! I don't know what mileage I get on any specific trip, I seldom fill up at the end of a trip except at the end of the travel season. I do know that my Alladin is better than Ray's, mine gives me 255.9 MPG (2 x 128 - its a function of the computer design, remember the early 64K computers ) down mountain grades! Sometimes I drive 70, sometimes I drive 50. I seldom drive faster than the speed limit. My target speed is 62 to 65 MPH on the interstate highways and slower on most federal and state highways. We have children and grandchildren in the Missouri, Colorado and California so we see our share of mountain driving. We've visited every state in the US (except the obvious Hawaii) and all of Canada with the exception of Inuvik and Newfoundland and we'll get to Newfoundland this year if the creeks don' rise!

The rig described below gives me 8.3 MPG. That is 133,526.6 miles divided by 16,055.9 gallons of fuel over the life of the coach, not a readout of a computer calculation.

Before this one we had a 38 foot 1994 Dynasty with a Cummins 8.3L. With 26,839.2 miles and 2960.8 gallons we got 9.1 MPG in the 2 1/2 years we drove her.

In both cases we had a diesel generator that runs off the main fuel tank and I have not compensated for that usage. Louse likes to have heat or cooling as well as lights TV and Internet. We have 120 V electricity on 24/7 when we are in the coach on the road. What we don't get from campgrounds we get from the generator. The 7.5KW Onan generator on our current rig has 1690 hours on it since we purchased it. We put 103 hours on the 5KW Kohler generator in the Dynasty.

[embo32]

Hi,

Just checked the vms on my 330hp cat C7, 40 foot 34000 lbs including tow car, 7.9 mpg overall burning 4262 gallons. I would say 90 percent of time I am towing. Cruise control set at 62mph, trans in 6th in economy mode is how I run on flat hwy. Mountains I cut back to 54mph and economy mode off. When I drive this coach with the cruise off I get less mpg.

See you out there.

Charles

[Fchandler3]

We get 7 mpg on our Allegro Bus with a Cummins 400 ISL. 40 feet long, 35,000 lbs, towing a Chevy Equinox that weighs about 4400 lbs. Usually drive 63-64 mph.

[OCwildlife]

We logged 10.2 mpg on our last 600 mile trip. 6 month old Tiffin Allegro 33aa, 35 ft. 340cummins. No towing yet. Very happy with that and my husband is pretty decent at math. Averaged above 10mpg for the last 2000 miles. Some trips including the steep Grapevine in California. Another trip up to Yosemite.

[lylefikse]

I would not have believed the difference in fuel economy good fuel can make. I had been filling up at our local Sams Club. After several partial fills I noticed our fuel mileage had fallen off to around 7 1/2. We had been getting closer to 9. On the advice of our neighbor, a long haul trucker, I filled up at a truck stop the next time we needed fuel. Our mileage went right back to 9. I had been saving 13 cents a gallon on the cheaper fuel. If you figure the difference in mileage, it would need to be 85 cents cheaper to break even on cost vs mileage. Now, I only buy fuel at Loves, Flying J, or Pilot. Run your own test but I am convinced fuel can make a difference. I wonder if the Sams I used may have had #1 winter fuel in the tank?

[wolfe10]

According to retired Petroleum Engineer I work with, most fuel for all stations comes from the same limited number of refineries. Yes, additive packages can vary to some degree.

But, absolutely, #1 diesel has fewer BTU's than #2 diesel. So if a station (any station that received fuel during the really cold months) still has #1 or a blend of #1 and #2 diesel, sure MPG will suffer. BUT, the difference in BTU's is only 2.5%. HOWEVER, the difference in Aerodynamic Drag between 70 Degree F air and 30 degree F air is 12%'. That is why most of us get the same MPG in the summer running the dash air as in the winter without it-- the factors offset each other.

The Caterpillar Corp document below is a VERY good read for any DP owner, not just Caterpillar.

http://forum.dieselrvclub.org/index.php/topic,6594.0.html

[wildebill308]

Brett, have you run any of the high percentage Bio blends? I saw 50/50 in Montana but bought the straight #2.

I have heard of problems with high percentage or 100% Bio.

What is your opinion?

Bill

[billandkarengerrie]

I run a 6V92TA DDEC IV with a V731 ATEC with O/D transmission. At 65 mph I average 7 to 8 mpg on an imperial gallon. Total weight with a 5000 lb truck in tow is 37000 lbs. I know it is a 2 stroke engine which isn't the most fuel efficient engine but not many are more reliable. I question some of the fuel mileage figures above. Some of the newer small motorhomes don't give the mpg's stated.

[wolfe10]

Brett, have you run any of the high percentage Bio blends? I saw 50/50 in Montana but bought the straight #2.

I have heard of problems with high percentage or 100% Bio.

What is your opinion?

Bill

Bill,

I run as close to zero bio as I can find. Fewer BTU's in bio, so MPG suffers a little. Shorter shelf life, clogs filters, etc.

[campcop]

+2.......I run as little bio as I can....I found that it foams a lot more than #2 too.....unfortunately, finding pumps with no bio are getting hard to find....

[wildebill308]

Bill,

I run as close to zero bio as I can find. Fewer BTU's in bio, so MPG suffers a little. Shorter shelf life, clogs filters, etc.

I am with you but it is getting harder to find stations without at least 10%-20% bio.

Bill

[wolfe10]

Ya, and you really have no idea in a lot of stations (and neither do most of the station employees), as many state: "Up To 20% Biodiesel"

[rossboyer]

We have traveled 90,000 + miles in our 2006 Fleetwood Expedition with a 300HP Cat C-7 engine. Usually we travel interstates because of the long distances on our trips cross country. We tow a Chevrolet Equinox everywhere and travel about 67 mph. Local highways 57 mph to keep in 6th gear in Economy Mode. Our average is 6.7 mpg.

[jleamont]

Here is an example of what I had discovered as the root cause of a no start condition. This is photo is from a B20 mixture in early March in South Eastern Pennsylvania on a customers vehicle. I seem to have lost the photo of the cartridge filter that was pulled, but it looked like someone buttered it. I avoid bio diesel, if I must use it in a pinch I always put an additive in the tank just as a precaution and only purchase enough to get me to the next fuel location.

[BearAndMoon]

We're in a 2003 Newmar Dutch Star 3802 with a 330 HP Cat. We get a consistent 10 MPG. Everyone that hears that, cringes. My reply is always the same. "Yep terrible mileage for a vehicle, but tell me, what kind of mileage does your house get?"

[Miramichi Cruiser]

We are running a 43' DSDP with a 400hp cummins ISL and Allison 3000 towing a CRV weighing in around 35k and 3,700 lbs respectively.

Based on fuel purchase and distance travelled on mixed terrain, we are averaging approx 7 +/- .5 MPG. I could probably get much better but alas I have lead-foot-itis!

[wigginsjsr]

We are running a 38' Monaco Knight with MaxxForce 350 HP, Allison 3000, towing 2008 Saturn Vue weighing approximately 4000 lbs. Unit weight 31,000.

Consistently get between 8.5 and 9.5 depending on wind and speed.

[trabuco]

We have a 40' at 32,000lbs with a Honda CRV around 3,500 lbs. My VMSPC reports an instantaneous MPG of anywhere between 2.6 and 256.0. But normally right 8.0 mpg.

[ncbounder]

Been reading this one as I am currently scheduled to take delivery of a new to us '08 HR Endeavor w/ 400HP ISL 8.9 next week. My gas Bounder has consistently averaged 7.00 MPG towing or not. The biggest difference with the gasser seems to be running the dash A/C..MPG takes a noticable hit then.

On another note...

We get a consistent 10 MPG. Everyone that hears that, cringes. My reply is always the same. "Yep terrible mileage for a vehicle, but tell me, what kind of mileage does your house get?"

Can't tell you how many times we've been pumping gas next to a car and we get the question "wow.. how much does it cost!?" My answer: "same as you $2.59 (or whatever) per gallon!" After that they'll either leave the smart alec alone or its the start of a good conversation.

[msgtnobody]

I just bought a 2008 Monaco LaPalma LX with the Cummins Diesel and Allison 6speed auto. Driving it home I got 11 mpg.

[Shellnut48]

8.4 MPG, Cummins 8.9L ISL, 400 HP, 41', 34,000 lbs, cruise at 60 MPH (MPG goes down sharply above 60), tow a CRV 3,700 lbs. Coming up on 30,000 miles and MPG has improved.

I keep a log of three versions of MPG at each fill up: MPG off the computer, straight MPG calculated from miles traveled and gallons used, and last and most accurate, MPG calculated factoring in amount of fuel used in the generator, Aqua Hot and when at an idle.

How do you measure fuel usage in the generator and Aqua Hot unit? I have a Tiffin Allegro Bus 45OP if that helps you.

[wolfe10]

Don't have Aqua Hot, so no advice on that.

For generator (Onan 7.5 QD) running one roof A/C I figure .5 GPH.