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Warpath · 05-16-2006, 08:33 AM

Could be hard to get an accurate answer since most of the lower HP motors like a 300 would probably be hooked up to a automatic trannie versus a manual or manual automatic that the bigger motors have. It would be hard to compare apples to apples.

I will say that my Cummins M11 350 hp & 1200 ft/tq with the original Fuller 10 speed averaged 11.5 mpg. That motor had 550,000 miles on it and well broke in. When I swapped the trannie to the Super 10 speed it killed my MPG & power quiet a bit. That might have returned as the trannie got some miles on, but by then I had sold it. My weights are probably pretty close between my new and old motorhome.

I hope to have my engine monitoring system later this week and I will have lots of info to give you once that is installed for my 300 hp setup now. If I remember I was getting approx 8 mpg when the engine was new and I think if I remember it creped up to 9 or 9.5 during one of my later trips and that was at 280 hp. It will be curious to see what the increase in horsepower does to my MPG.

05-16-2006, 08:33 AM	#3
Warpath Senior Member Join Date: Aug 2002 Location: N.E. Ohio Posts: 768	Could be hard to get an accurate answer since most of the lower HP motors like a 300 would probably be hooked up to a automatic trannie versus a manual or manual automatic that the bigger motors have. It would be hard to compare apples to apples. I will say that my Cummins M11 350 hp & 1200 ft/tq with the original Fuller 10 speed averaged 11.5 mpg. That motor had 550,000 miles on it and well broke in. When I swapped the trannie to the Super 10 speed it killed my MPG & power quiet a bit. That might have returned as the trannie got some miles on, but by then I had sold it. My weights are probably pretty close between my new and old motorhome. I hope to have my engine monitoring system later this week and I will have lots of info to give you once that is installed for my 300 hp setup now. If I remember I was getting approx 8 mpg when the engine was new and I think if I remember it creped up to 9 or 9.5 during one of my later trips and that was at 280 hp. It will be curious to see what the increase in horsepower does to my MPG. __________________ 2012 Showhauler 28'6" Motorhome on a Columbia w/ 450 Mercedes.