Anyone have any comments or experience with a Freightliner Columbia Chassis paired with a Mercedes 450 engine and Allison automatic?

No experience with the mercedes but the truck and tranny are awesome. Mine is a 515 detroit with the 10 speed full auto and it drives wonderful

I'm running a 43' stretched Columbia chassis with 450 MB and 10 spd Eaton autoshift. Driving 70 with no trailer it will do 10mpg (running aprox 70mph). Have logged less than 5k miles so expect the milage to go up when it loosens up a bit.
The Eaton auto shift is great but without a trailer the lower gears are overkill. Better to put it in the manual mode to upshift from a stop.

We have the 450 with a Meritor 12 speed. IT'S awesome. Our best mpg is 11.75 and we average 10.5. not bad in my opinon

Thanks for the input.

I've heard a lot of Freightliner bashing in the past and wondered how much of it was just bias and how much is real.

I've got a Renegade 45' on a Columbia with a 450 Mercedes and only get 6-7mpg towing a Jeep at 74mph. What gives? Does that 4mph really affect mileage that much?

Ouch, we used to tow a 2500 pickup crew cab and still got 10.5... I don't go slow either.

Try running 68-70,...of course a headwind, hills, & running on interstate hwy's (vs 2-lane roads) are all going to have an effect. You might also check & see what rearend gear ratio you have. Most truck conversions were spec'd out to haul "monster" stacker trailers full of iron, therefore came with lower geared rearends.

You may be on to something with respect to the rear end gear ratio. I originally bought it with an 11,000 car hauler. I'll look into it. Also, what RPM is your engine running at 74 MPH?

Dan, I don't know the exact rpm, but would guess something around 1350 @ 75

Dan,
My century has the 14L 470 detroit with the autoshift. At 75 mph we are turning 1550 rpm. we still get only around 7mph. running the twin screw effects it alot as well as turning that many rpms.
Wick

That sounds about right. At 74mph I'm right at the edge of the green arc, about 1600rpm @ 6.8-7.3 mpg. I don't have as aerodynamic fairing over the cab as you do though.

I can't get those numbers either. I experimented the last time that I had the rig out. I finally got 10 mpg, but that's without the generator and keeping it in an rpm range just slightly above 12th gear kicks in. I don't recall the rpm's, but I was doing a little under 65 on flat ground and a reasonably full normal load. I was also falling asleep at the wheel at that speed.

.....68 mph = 1450 rpms.....gets anywhere from 8-10 mpg.....any faster and I get tickets......really don't care about the fuel mileage.....I spend less than a grand for all fuel- lawnmower, trucks, car and house in winter...at this time thats total about 8% of my income a month so it hasn't bit me in the shorts ....yet!......geofkaye