phughes69

I took a short trip recently to pick up a engine parts wash tank and used my truck to get it. My truck is a 1996 Chevy C3500 extended cab dually 6.5 turbo diesel with the 4L80E and 4.10 gear. Running with no cap on, @2200 rpm at 65 MPH I averaged 13.56 MPG That was 210 miles of freeway and 20 of city. Temperature conditions were 30-35 degrees, with slight wind, with nothing in the bed. The motor is completely stock except for a 3" down pipe transitioning to a 4" pipe to the rear, and a K&N cone filter right on the front of the turbo. The truck has 114,000 miles on it and I just had an alignment done. Years ago I checked the mileage and it was about 15 MPG. . If it wants for the fact that this thing is paid off and I only use it to pull the boat to the launch ramp a mile away, I'd get rid of this thing.
What kinds of mileage are other chevy 6.5 TD owners getting

MILD THUNDER

iTrader: (3)

I cant speak for the 6.5L Diesel, but I have a 97 K3500 454 dually with 4:10's. Best ive seen on a long hwy trip is 13.4 cruising at 70.

I thought the 6.5 would do better than what you got. But, winter fuel blends and wind conditions can make a big difference in economy.

Jupiter Sunsation

Check the spark plug gap!


Seriously though check the fuel filter. My Duramax would plunge in mileage if the filter was bad (like wow, got 250 miles to that tank, better change the filter again!). My 2500 crew cab 2WD would get about 17 as the best mileage, usually in the mid teens. These guys that claim 20-25+ must be relying on the computer calculation not hand calculated at the pump.

My method was, fill the truck almost to the top of the filler neck, reset trip odometer,drive it X miles and refill it again. Take the miles driven divided by the gallons bought and that was the true MPG. 325 miles burning 20 gallons of fuel = 16.25 MPG.

Not that it would change the average but the CC GM trucks with the short beds only have a 26 gallon tank (vs. the 31 in the long bed version) so I never got much past 400 miles and was looking for a gas station. Twice it ran out of gas and the light never came on, needle was low but I was waiting for the light!

Sydwayz

iTrader: (1)

Did you get the higher mileage with the stock air filter?

Many people think that a high flow filter nets you better fuel mileage. Not the case.

More air means you need more fuel for combustion to take place.

wannabe

Phughes- These engines are not known for being very efficient. The 13.6 mpg vs 15 is not that far off and weather conditions can play a factor, especially wind.

I don't know what to tell you except that a 8.1 gas engine is about the same. I get 13-14 on the highway and 12 around town in my 2500 Avalanche.

Wannabe

phughes69

Wannabe. That is part of my ***** too. Even if mileage with the 6.5 is slightly higher that the 454, it becomes a wash once you factor in the higher price of diesel. Plus there are more tweaks that you can do to a gas BBC than a 6.5 for a lot less money.

wannabe

THE 6.5 is an older design, based off the 6.2 diesel. I remember driving a 6.2 Sububan 4x4 up north to deer camp with my father back in 1984. This was the old square suburban and the thing was a pig, wouldn't get out of its own way. The 6.5 was an improvement, but not much.

Have you looked at Hypertech tuner? I have one for my 2500 Avalanche.

Our handyman has a 2002 Duramax 2500 pickup, 280k miles. He gets 15 around town and 19 highway unloaded. Thing is noisy as hell, rode with him for a 1 hour trip-wow. Now the newer ones are much quieter. But he does have pulling power

Wannabe

FIXX

iTrader: (2)

we can go from elgin il to hurley wi on 18 gallons of fuel..325 miles,,about 18 miles to the gallon..1997 k3500 4x4,300 k..

gm reccomends injector replacement at 100k,also if your turbo psi output is not up to snuff the truck will eat more fuel because your putting you foot more in to it.the truck above also has 235/80/16 tires which brings the rev's down on the highway..75 mph the truck is at 2300 rpm.s.....also thease trucks are common for the brake switch to ware out...your transmission wont go into lock up..get the truck up to 65 mph and lightly tap the rake pedal,the tach should jump 200 rpm's if it dont then your switch is bad..

im suprised you have not replaced your injection pump yet..those are common to go andif you did have it replaced that could be another reason for bad fuel milage if the pump's timing is off even 1*..i know thease engines inside and out so feel free to ask ??..also is their any black smoke out the tail pipe?

Tinkerer

I have the 93 2500 HD 6.5 TD sith 4:10 gears FWD - I am getting 17 miles to the gallon, 11.5 pulling the boat
12,000 LBS

Tinkerer

SYDWAYS - I am not sure that is correct with the turbo diesel. I did a lot of mods to mine and it did nothing to the MPG. Sure increased the HP.