Ok, which gets better fuel mileage pulling flatbed? Same specd truck same load same driver? Anybody have experience?

TMC- Des Moines is running several hundred Cat 475's and is reporting many drivers getting over 6 mpg in their flatbed operation. 13 speeds with 3.36 ratio's I believe.

Oh yeah, both pre-emmisions too. I just got rid of an '06 379 with 3:55's a 13spd and a 500 ISX. I finally broke 5 mpg running from Phoenix to Salt Lake empty.
My next truck will be a 379 or a W900L with 3:36's just trying to do a little more research on the engine. I've talked to drivers that live and die by either one.

Expecting high mpg numbers out of a rolling windblock like the 379 or W900L is a longshot in itself.

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The Cat costs more to buy but gives better MPG because the cumming has the EGR set up.

I'm not expecting "high" mileage. I would be happy with 6 mpg. Anything more would be sweet. Before I had the 06' I was in an 03' with a 550 cat 3:36's and an 18 and was at 5.5 on average and I could run all out from Salt Lake to L.A. (75-80) in Ut. and NV. In the 06' at 65-70 for 720 miles I got 4.8 at best and the worst was 4.1

I have an 2005 Kenworth T800 with 475 CAT, meritor 12 speed autoshift, michelin X ones, 3:36 gears and 180,000 miles. According to the trucks computer I have averaged 7.26 mpg for lift of truck. Have 9 % idle.

If you want to post your truck and details maybe I can help you figure it out. Just how fast do you normally run?

I have a 2007 Peterbilt 379 with a 475 Cat C-15 Acert twin turbo. The truck has about 64,000 miles on it and the trucks computer shows an average of 5.8 mpg for the life of the truck. I'll admit, I was skeptical going to the twin turbo from the pre-emission Cat, but I am very pleased. The truck pulls hard and gets great fuel mileage I think. The set up I am running is 18 speed Eaton with 3:36 rears.

Folks, don't listen to the computer, it only works from preset variables, and not real world. Fill the tanks, run normally, refill tanks, calculate gallons versus miles driven. Get the actual, not the estimated.

I drove an 06 T600 with a twin turbo C15 Accert, and when it wasn't in the shop, I was lucky to get 5 mpg out of it. The computer said 6.4, I only idled on warm up and cool down, for better than 100k miles. Lost both of those pricey turbos at under 100k miles, lost all of the valve actuators in those three fancy heads, and had the computer #### out on me. Now you couldn't give me a CAT.

I currently drive an N14 Cummins, with 650k miles on it. I average 5.8 mpg actual, and I haul oversize loads. I don't idle much, but I do have a webasto fuel fired heater, so that eats a gallon or two a night...

I will stick with Cummins, but it's all a matter of what you need, what you prefer, and what kind of loads you are going to haul.

If you are concerned with fuel economy, go detroit.
If you want power and grunt, go Cat.
If you want a nice mix of the two, Go Cummins.
Then take that Cummins to pittsburg power and take that CAT's doors off. lol.

Cummins dabbled with twin compound turbos with the NTC-475. I believe they found them to be rather unreliable in regular service. I guess history repeats itself.

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