mx3500

Re: a 2007 Chevy express 3500 4.8 liter 3:73 4 spd HD Trans. I started with a full tank with 2 bottles of fuel treatment and drove 70 miles today taking it very easy on the highway 60-65 mph, yet it still took 5.5 gallons of gas to refill the tank. This vehicle has extremely low miles, but what a pig! 13-14 mpg going slow on the highway!!! Does anyone know what highway MPG it should be rated? Last week I had to drive to phoenix with speed limit on hwy 10 is 75 mph (I drove 80 mph) and the mileage was horrendous- I could practically see the needle moving. My front tires are 70 psi off road and rear 80 psi. Could off road tires be the problem or something else??? Ouch!

mx3500

bump-

ExpressvanMan2000

I mean 14, 16 mph sounds about right its a 3500 v8 2007 chevy van

mx3500

I seen online these express 3500 were rated between 18-20 mpg highway, mine is nowhere near that not loaded & with less than 10k miles on it I would expect at least 18. My 2003 1 ton e-350 ford with a 7.3 diesel loaded gets way better mpg and it has 340,000 miles. Maybe the diesels get better mpg but I assumed the other way around. The big diesel trucks (med duty & 40 ft RV) I drove got 6-7 mpg but they were pulling a lot of weight.

tech2

65mph isn't slow. the thing has the aero of a 4x8 plywood sheet. the rating test cycle isn't done driving 65mph. slow down to 50 and see what you get.
diesel engines are 30% or more fuel efficient that a gasser. Any money you save in fuel is offset by higher maintenance and repair of a diesel engine.
this is the rating for a 5.3 but won't be far off a 4.8L
2007 Chevrolet Express 1500/2500 2WD (fueleconomy.gov)

mx3500

Thanks for the link. Given this is a 3500 with off road tires, it could drop their rating down to 12 city 16 hwy, and if rating is based on 50-55 mph even more so. Maybe the 4.8 gets slightly worse mpg than 5.3, but I thought by adding fuel additives/injector cleaner the mpg would be in the upper range. I haven't checked without, for all I know it could be worse than 13 without the additive. I'll be getting it checked out soon. Any recommendations to improve fuel consumption such as different air filter, tuner, etc? (Driving 50 mph won't work out here on the single lane hwy with mostly no passing.)

tech2

stay with the rated fuel....using premium in a 4.8 will do nothing as its not a high compression engine. It actually slows stock class racers down at the track. at every oil change put a injector cleaner in the tank as preventative maintenance. to clean dirty injectors you need equipment...tank additives don't fix problems.

William Kisselstein

When I first got my 2500 on the highway it got around 17 on a 150 mile trip, even with a warped rotor. The 3500 was never that good, but it sat a little higher and it was an extended wheelbase. Yours is the next generation and in theory should be equal or better.

I don't think you can judge from just one trip, though. When you buy gas get a receipt and write the odometer reading on it (and how full if you don't fill it up) and keep track over a few weeks. That will give you a more accurate sample.

A diesel will get better fuel economy. But you have to do the math, when I considered going diesel the additional economy did not offset the higher price of the fuel.

tsoleno

I've never actually checked, but the trip computer on my 08 2500 4.8 pretty much stays at 12 MPG loaded.