Curious to the difference in fuel economy between a 350hp and the 450hp. I know there are a lot of factors. Hoping to hear from someone who has owned both so driving habits would be the same.
Jerry
About 1 mpg difference, but also much heavier, probably nearly 9,000 pounds more
Fuel burn is controlled by your right foot. When I upgraded my ISM450 to the ISM500, I strongly believe with the resonator change also, the fuel mileage improved. Over known distances I consume the same amount of fuel, but arrive quicker, so if I drove the exact same, no doubt the mileage would be better.
That is my story and I'm sticking with it. ;D
I am also about one mpg different but my old coach was 34 and this one is 42 foot. The grand Cherokee cost me a half a mile per Fallon over the wrangler too.
My VMSpc reports our ISM 11 450hp, 2001 U320, 36' FT has gotten 8.0 mpg over 65K miles (since the beginning of engine time). Three drivers, two different tows, flat lands, mountains, back roads, slow roads, hilly roads, lots of small town roads, everywhere. Same coach as Dave M but without the hot rod mods (yet)
A light load, no tow 63 mph drive from CA to MN probably with a tail wind got us 9.4 mpg over 2400 miles.
I like the additional power towing especially out West. For our 8,000 miles or so per year the difference between 9 and 8 mpg is just over 100 gallons per year or about $400.
Roger
We're seeing 8.4mpg over 131,000 miles and 4 owners on our 40 ft 1999 M11 towing
best, paul
Sounds like not a whole lot of difference then, unless you start towing heavy.
My 280 with turned up 8.3 got around 9.3 going to New Mexico and back. Doubt we can pull quite as much as a big 320.
Our 1990 U280 with Cat 3208T gets between 9.3 and 10 mpg at 75 mph on the interstate.
It's only 250hp. That said, it accelerates faster than our "new" U320 400hp M11 - I'm checking to see if it has a hole in the tank--- it gets about 7mpg. Our Toad is a 2000 Jeep Wrangler.
Weight matters! We almost never see 75mph, 65 is normal cruise speed for us.
When I started towing, my fuel economy improved about 1mpg.
My towed is somewhat heavy, but my speed slowed from 65 to 60.
My ISC gets 8 MPG average pulling a 4dr Wrangler at 65-68 MPH. Curious to see what happends now that we are live aboard and a good bit heavier.