Diesel Mileage (Miles Per Gallon)

[C.Martin]

Got out the sharp pencil...

I have kept a spreadsheet since new...and we now have just over 33,000 miles of data.

I had been using total gallons and total miles and seeing 7.5 to 7.6 mpg. (ISL 400hp)

Today I subtracted the estimated fuel used by Oasis...figuring .44 g/h times the hrs meter...and Onan QD8000...figuring half load rate of .49 g/h.

With these corrections applied...I am getting 7.8 mpg....pulling our JKU.

I feel so much better now... LOL

[Crasher]

I have not read all of the previous 169 posts, so maybe someone has beat me to it. Most diesel engines will use between .38 and .45 lbs of fuel per hp hr. The amount of hp required is dependant on weight, rolling resistance (wind) and speed. Lets use .42 lbs of fuel/hp hr as an average. If it requires 150 hp to push the MH 65 mph, it would require 63 lbs of fuel in one hour. At 7.1#/gal, the engine would consume 8.87 gallons of diesel in 65 miles. 65/8.87= 7.32 mpg. It really doesn't matter what someone else gets for mpg unless both MH's weigh the same, are geared the same, have the same rolling resistance and travel the same speed. If you want to find and compare a future MH with the best fuel economy, find the lightest one that fits your needs with an engine that has the lowest fuel consumption per hp hr. Then you control your mpg by the way you drive.

OR, as most of us have done, find a coach that trips your trigger and fill the tank when it gets low.

[AE Wanderer]

Our 2008 American Eagle 42F with a Cummins 8.9l, 425hp, ISL, is getting 5.9mpg.

Coach last weighed in at 39,950# with a 3500# toad.

[lwmcguire]

Milage in an all electric coach is usually like chasing a blond steer

The Aqua-Hot and generator both draw out of the common tank

This is in addition to all the other variables and I find the wind speed and direction to be a huge variable

We tend to use both the gen and Aqua-Hot at some point during traveling

Milage considering all that varies from 7-8 at 65 mph typically

[tropical36]

Originally Posted by AE Wanderer

Our 2008 American Eagle 42F with a

Coach last weighed in at 39,950# with a 3500# toad.

Sounds closer to the truth, than many, IMO..
According to my digital readout over the last 12yrs, it's 6.2 and it took me 3.5yrs for bringing it up another 0.1. That's probably not taking the genset into account either. Don't have the extra expense of DEF, however and something that needs to be taken into account, as well.
Rig weighs in at 32K + and pushed with a 400HP Cat C9.

[Damion]

Took a little drive to Alaska this past summer. 2003, 8.3 ISC 350 Cummins Total Stock, Towing 2015 Equinox, Total weight 32,000 Lbs. Deducted .5 GPH for 7.5 KW Onan Generator.
Have the spreadsheet to back these numbers, "For what it is worth"
9,365 Miles Total
1336.2 Gal Fuel (Liters converted to Gal.)
$4,452.64 Cost (American)
$3.33 Per Gal Avg Cost
7.64 MPG Avg
5.5 MPG Lowest
7.9 MPG Highest

[APhotoWizard]

My 2001 Tiffin bus 32000 pounds with jeep grand cherokee and 170,000 miles shown 7.6 MPH on the computer. It seems we have finally answered the question, what is you mileage. As a side note, I had the "opportunity - don'ask why)" to drive my rig for about a month without a tow vehicle. My calculations show it gets about 1/2 mpg better without a tow vehicle.

i like the suggestion to take to the road, and fill it when it gets low.

[PandS]

8.0 MPG average over almost 27,000 miles in our 42,500 lb Coach, towing a CRV.


We are not "lead footed". Generally between 1600 and 1750 rpm in 5th or 6th gear when traveling. Virtually no in town driving. We do that in the Honda. YMMV. -Paul

[winniman]

I have the 5.9 , 24 valve 2000 275 hp cummins in a 38 ft DP. My scanguage and math calculations work out the fuel mileage at around 11 mpg. It would be slightly less with the tow car. My gross vehicle weight is around 25000 lbs, although I am likely less than max. We did a two month tour last summer, and used $4200 dollars in fuel. If I only got 6 -7 miles per gallon, those fuel costs would have been considerably more. I am happy with the little 5.9. It is faster than my previous gas rv of the same length with the v 10. I don't lack for power in my opinion, and the extra cash can stay in my pocket. Im sure if I upgrade in the future, I will miss the 5.9 at the fuel pumps. We travelled with a friends rv as well. His rv is a 2007 40 ft, with slightly higher weight. I think his gross weight was around 27000 lbs. He has the 5.9 cummins with 300 hp, and the common rail fuel system. When we would fill up, my rv would use less fuel than his. I would say if you discount the extra weight of his rv, and his slightly larger tow vehicle, both 5.9 cummins would be similar in mileage. I guess if you cant have the biggest, or the fanciest, at least us 5.9ers have some claim to fame. They definitely are the mileage king of diesel pushers. If you travel on a budget, spending thousands less on fuel is a good thing.

[PandS]

I had the 210HP version of the 5.9 (6BT5.9M) in my 30' Downeaster boat back in the late 80's and early 90's. It was really fuel efficient! 7.4 gallons per hour at 18 knots at 2200 RPM, 5.2 GPH at 15 knots AT 2000 RPM. Top speed was 21.3 knots at 2600 RPM. Unbelievably reliable, as all I ever did was change fluids and filters during over 1600 hours of tough duty as a Charter Fishing vessel. GREAT engine!-Paul

[Dutch Star Don]

I've kept track of mileage over the years and my really light weight 2005 Diplomat with a 400 ISL with propane heating COULD get in the low 9's on a flat, straight, windless road where I didn't stop or slow down for 300 miles. But, it typically saw the low 8's.

Fast forward to a 10K heavier DP, flatter front end and dragging a tag axle, my mpg over 5 years was low 7's.

Now with my 2019 DP weighing in at 42K and towing, I'm getting in the high 6's, and on a good day, low 7's. I'm at 12K miles and hope to stay in the low 7's once I get the engine to 15K.

My point, I think when many brag about their fuel economy, they either guesstimate how many miles they drove and roughly figure fuel or brag about the one time they got 10 mpg on the downhill side of a mountain and then neglected to fill the tank all the way because they were not level during fueling.

All of us who own a DP know exactly what they're getting if you track it over at least 1000 miles. So when someone comes on here at makes an outlandish statement, they should realize that they're not talking to someone that has no idea what a DP really gets. I think they forget that they're talking to an educated crowd of DP owners.

[WILDEBILL308]

So here are some real world figures. This is for a 2003 Bounder 5.9 diesel. I keep my records on gas buddy. these are for a year. Your mileage may vary as they say. I know my mileage is always related to wind and driving conditions.
2014. 10,289 miles 8.75 mpg
2015. 6,422 miles 8.37 mpg
2016. 9,085 miles 8.63 mpg
2017. 2,741 miles 7.82 mpg
2018. 5,801 miles 10.58 mpg
2019. 8,820 miles 8.73 mpg
That makes a total of 43,158 miles with a average mileage 8.81. I think that is pretty good as I am always towing.
Now I get to start over with a much heavier coach (2008 Mountain Aire)
and a ISM. Would like to see 7 mpg but we will see.
Bill

[Scottybdivin]

Originally Posted by WILDEBILL308

Now I get to start over with a much heavier coach (2008 Mountain Aire)
and a ISM. Would like to see 7 mpg but we will see.
Bill

You're right. an ISM would like to see 7, but only under the best circumstances.

[MO Fred]

So far.... having our coach for two years and putting close to 20k miles on it with toad, we are getting 8.4 MPG with the C12 CAT.