300HP Cummins fuel mileage

[motofamily]

I am curious to see what the average fuel milage is for a 300HP Cummins motor in a pusher. Ours is a 2006 model and I am not that happy with what the info center is telling me I have not really kept track of fuel milage in the past because 90% of the time we are running the generator and it really makes me mad to waste money but I feel like I should be getting at least 9-10 mpg my info center says 7.2ugh maybe my foot is heavy, or maybe i need to change my fuel filter or air filter or wallet filter. ANy help ideas or input would be great.

[H. Miller]

Note the recent thread "275hp vs 450hp" which has some good info.
DP weight and toad weight (if applicable), driving speed, etc. are all unknown variables which affect mileage.
Our Cummins ISC @ 330HP with full Banks kit (+115hp) with 32,000gvw and Saturn Vue toad gets high 7's for mpg. Speed is normally 60-65 mph.

[40DS04]

We have a 400HP Cummins ISL and recently completed a 4,000 mile swing throught the Rockies and Southwest. I calculate mileage using gallons purchased and miles driven. We consistently average 9MPG, with 33K loaded weight and Jeep Grand Cherokee toad. I love this thing!

[Gary RVRoamer]

9 mpg on an ISL is incredible! We usually manage 8.1 if the mileage is predominantly interstate cruising (60-64 mph) and that is better than most others I hear from.

[Gary RVRoamer]

7.2 seems low if that is highway cruising, but about right if much of it is lower speed town traffic or even two lane roads through towns.

And a heavy foot will do it too.

[deandec]

7.2 mpg with our 300HP, C8.3L, Cummins mechanical in a 31,000 lb MH towing a Jeep GC.

That is an 8+ year, 50,000 mile average including lots of mountain grades, short trips, 500 hrs generator use, and some long flat land runs.

It does seem we are going into the wind and uphill....both ways all the time.

[skipwil]

I have the '01 ISB 300 w/Banks Ottomind . The Cummins computer showed 10.21 when it was last checked. 3mpg better than the w/h 8.1.
Safe journeys

[wkdwitch]

Our '03 ISB 300 averages 9+/- the best is 10 the worst is 7.5 climbing and loaded. BUT, we drive 59 mph and are 36ft/26k. I drive like a granny, but am not one.

[Gary RVRoamer]

The lifetime average recorded by my 2004 ISL is 7.55 mpg. It was 7.15 when we bought the coach (used) in late 2006), but it has been climbing steadily. Probably a combination of a lighter foot and more interstate cruising. I often get 8.1-8.3 mpg cruising at 62-64 mph, but two lane highway driving knocks it back to 7.2-7.6.

[Roadking52]

Last time I checked mileage on '02 ISB 300 pulling Vitara toad and running generator for a/c was 8.5 mpg. This was predominately interstate highway at 65 to 70 mph. 32 foot Itasca Horizon. Your mileage may vary, etc.

[FleetMan]

ISB 300, two seperate trips from western WA to the north east, down to Texas and back. 14,500 miles total towing a 4,000# toad, I try to drive about 62 mph. High was 10.175, worst was 8.146 - Caldwell, ID to Troutdale, OR with stiff headwinds along the Columbia.

[greystroke]

My 275 has a lifetime mileage of 10.5 for 75000. Since I bought it last year my wt is about 23000 loaded plus a 4000 lb toad I have been getting 10-11 while driving at 60.

[RV'nOldTimer]

Over 49k miles at various speeds but mostly around 60+ mph, our 300 hp 5.9L cummins has averaged 9.5 mpg. This is with a Saturn toad. Our 32T is lighter than most DP, however.

[Shuffster]

I am about dead on with wkdwitch. Computer shows lifetime 9.2 mpg with 22K miles (regularily cross checked with fill ups) 24,000 lbs plus toad.