Terrible Fuel Mileage

[singularity]

I just bought a new to me truck. It's a 98 GMC K2500 with a 350 and an auto. I filled the tank the first time and got 12.85 miles per gallon with 80% freeway at 70 mph. I filled the tank the second time and got 12.84 mpg while doing the same 80% freeway but only 60 mph. It just passed smog, and I always accelerate gently. What the hell is wrong with my truck?

[revrnd]

What's the axle option on the SPID label in the glovebox? If GT5 you've got 4.10s. On my '04 w/ 4.10s & running anything faster than 70 isn't pretty gas mileage wise. What RPMs are you running @ 60 & 70?

 

Or the gears may have been swapped for something lower (larger numerically).

[old-chevy-dude]

seriously?

 

it's a 12 year old 8,000 pound truck.. 12.84 mpg especially on winter gas is pretty good, for a truck that old..

[txab]

What mileage are you expecting to get?

[KMGZ400]

thats 100% normal... what the hell are you expecting out of a 12 year old truck with a 350?

[mxdirtrider56]

seriously?

 

it's a 12 year old 8,000 pound truck.. 12.84 mpg especially on winter gas is pretty good, for a truck that old..

 

+1 If my 94' got 13 mpg I might get out of the truck and do a little dance.

[matsrat]

if you want mileage. buy a half ton. that sounds normal. 12-14mpg is good. its a 3/4 ton.

[markw8]

Sounds pretty normal. The best thing to do is not check the mileage, just fill it when it needs it.

 

Mark

[revrnd]

Sounds pretty normal. The best thing to do is not check the mileage, just fill it when it needs it.

 

Mark

 

X2

 

That's my motto over the years. I've got the truck that does what I want it to do. If I worried about the mileage, I'd be still driving a S truck.

[singularity]

What's the axle option on the SPID label in the glovebox? If GT5 you've got 4.10s. On my '04 w/ 4.10s & running anything faster than 70 isn't pretty gas mileage wise. What RPMs are you running @ 60 & 70?

 

Or the gears may have been swapped for something lower (larger numerically).

 

Yeah, it's got the GT5 code. It turns 2000 or so at 60, and 2500 at 70.

 

Honestly, I didn't expect 25 mpg out of this truck, but I expected better than 12.8. My brother has a 71 Chevelle with a carbureted 350 and a turbo 350. It gets 20 mpg. Then again, it does weigh 2000 pounds less than the truck.

[ryan_hermanutz]

What's the axle option on the SPID label in the glovebox? If GT5 you've got 4.10s. On my '04 w/ 4.10s & running anything faster than 70 isn't pretty gas mileage wise. What RPMs are you running @ 60 & 70?

 

Or the gears may have been swapped for something lower (larger numerically).

 

Yeah, it's got the GT5 code. It turns 2000 or so at 60, and 2500 at 70.

 

Honestly, I didn't expect 25 mpg out of this truck, but I expected better than 12.8. My brother has a 71 Chevelle with a carbureted 350 and a turbo 350. It gets 20 mpg. Then again, it does weigh 2000 pounds less than the truck.

 

 

And the aerodynamics is somewhat better than our bricks.

[KMGZ400]

i wouldnt think you would get 20mpg out of a 71 chevelle...idk maybe im wrong

 

 

mmm 71's the second best year NOTHING is better then a 1970 chevelle SS 454

[mxdirtrider56]

Yeah just remember your truck is really heavy. Those older ones tend to suck gas around that speed too. When I do take my 94' out I tend to keep it at 65 mph and below because anything above that drops the fuel gauge quicker than I can blink my eyes.

[cghbuilder86]

keep it to 55 and you should see improvement

[txab]

Does your truck have stock size tires on it?