Yall see my sig, I have 3.54's and 335 85 r16's. I get 14mpg on a grandpa driven tank. is this right? I also just saw that the top of my tank is leaking and all around the sending unit is nasty with diesel, the leak doesn't make it to the ground though. could I be leaking that much? or is 14mpg normal?

 

dont forget to add the additional distance traveled by a bigger tire... take the diameter of your tire, divide it by the diameter of a stock tire and multiply that number by the number of miles you traveled and that is your actual mileage traveled.

 

What he said.. It makes a big difference.

Also, putting your AFC foot back in should make a little difference too.

 

ok so 335 divided by 315 times distance traveled, thanks. And the truck has always gotten this mileage since it was bought with like 28,000 miles. I have never ran 315's on it though, and it was stock up until around 126,000. thanks for the help yall

 

I would think that the truck came with 265's stock so the speedo would be set to that size tire. I would think if you did the math figuring 265's instead of 315's then it will make a bigger difference.

You could also check the inside of your door to find out what the factory size was.

 

No. 335 and 315 are the widths of the tires. The height is figured by the second number, say in a 315/75/16 the sidewall height is 315mm*.75 then convert the product to inches, multiply by 2, and finally add 16 for the height of the wheel. If you want to make it easier most online tire stores have calculators where you input the tire size and it will give you the diameter in inches.

 

I always get that F-ed up . Here is a link to a calculator http://www.tirerack.com/tires/tirete...e.jsp?techid=7

 

He's got a 3500, means it came with 235/85's stock. I'm guessing that's a typo, and you really meant you're running 235/85/16's.

A 315 would be a MONSTER, and 4 of them on the rear would surely destroy your mileage.

 

Yeah I did mean 235's, I guess I'll see at next fill up. Ill let yall know on this thread. thanks for the help

 

Well, since we got the tire thing squared away what's your timing set at? It's not mentioned in your signature...

14MPG is definitely not right, even for a dually. My dad averages 20mpg highway/little city driving and he's a "grandpa driver" as well.

Other than that, fuel and/or air leaks are the only things that come to mind.

Shawn

 

He's got an Automatic! (Assume your dad's is not?). 20 is high for most autos (especially since ULSD) but still should do 16-18 mpg!

I just babied my 02 for 500 miles, due to new head and turbos. Keep it under 15 psi boost.
Was a bit disappointed to only get 16.8 mpg. That's about what I usually get on my 1,000 mile checks.

RJ

 

Well I got six 37x12.5's on my truck. Those are 318/82 R17's. Total of 13" lift.

I've got 14mpg on town and 17 to 19 mpg on highway.

Depends how I drive.

 

I have a 99 3500 5sp S&B cold air and 4inch exhaust and 235x85x16 and i am getting 22.5.