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Old 03-19-2005, 05:31 PM   #1
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Can anyone out there with a 400hp Cummins (preferably on a 43' MH) provide information on your average fuel economy?

We're stepping up from a 300hp 40' MH (which gets around 9 mpg)to a 400hp (Cummins ISL) 43' Mountain Aire... and with fuel prices rising so rapidly, we'd like to have an idea of what we might be getting ourselves into.

Thanks!

- John
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Old 03-19-2005, 05:31 PM   #2
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Can anyone out there with a 400hp Cummins (preferably on a 43' MH) provide information on your average fuel economy?

We're stepping up from a 300hp 40' MH (which gets around 9 mpg)to a 400hp (Cummins ISL) 43' Mountain Aire... and with fuel prices rising so rapidly, we'd like to have an idea of what we might be getting ourselves into.

Thanks!

- John
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Old 03-19-2005, 08:10 PM   #3
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....12 in my Volvo tractor loaded to 30,000#...t hen again I'm not a square brick....areo truck and v nose trailer....geof kaye
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Old 03-20-2005, 01:22 AM   #4
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John & Peter, I would say not to except any more than 6-7 maybe 8 mpg according to what other owners have said. Ed. S
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Old 03-20-2005, 04:44 AM   #5
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Towing our GMC Yukon XL toad we get about 8 - 8.5. Remember a diesel will have a sweet spot at around 2000 - 2200 RPM that will be the best mileage, then if you go above that spot by a mere 100 RPM you can loose 2 MPG.
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Old 03-20-2005, 06:18 AM   #6
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Thanks, all.

Guess we'll just have to wait and see!

Foz: we'll definitely look at performance in that 2000-2200 rpm sweet spot.
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Old 03-29-2005, 09:05 PM   #7
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What speed are you going at the 2000 to 2200 sweet spot? My 02 40' Allegro Bus with a 350 Cummins is turning 1840 at 70 MPH. It does 68 MPH in 5th gear at 2150. I think I would have to break most speed limits to reach the sweet spot in 6th.
Later ...Harry...
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Old 03-29-2005, 09:27 PM   #8
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I thought the RPM that the engine makes the most torque would produce the best mileage. My ISC makes the most torque from 1300 to 1600 and according to my VMSpc that seems to be where I get the best mileage. 2000 RPM is pushing the big barn door pretty close to 80 mph , and at that speed I'm sure my mileage will not be good.
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Old 03-30-2005, 04:49 AM   #9
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The biggest factor is the wind resistance, which increases exponentially as the speed increases. There's a big difference between driving at 60 versus 70. Unfortunately, I didn't by a coach with a Cummins 400 to drive at 60 so I pay at the pumps.
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Old 04-05-2005, 12:48 PM   #10
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With 5,000 miles on mine, my overall average is 7.4 mpg. Most of my driving is interstate and I'm usually cruising around 60-65...
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Old 04-05-2005, 12:50 PM   #11
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Opps, I forgot to upgrade my profile... 2005 Allegro Bus with Cummins 400
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Old 04-05-2005, 05:46 PM   #12
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I had a B series 24 valve that had a sweet spot ( more power better fuel mileage )according to Cummings at 2,400-2,700. This was a 24 valve engine. THe engine manufacturer can give you the skinny on hte sweet spot. My current 12 litre 400 likes to run at 1,400-1,600 this is between 55 and 70 mph
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