hello im new to the hole diesel world,i just recently purchaced a 86 f-250 4x4 w the 6.9 idi and know nothing about it. im getting about 10 mpg not loaded,there are no aftermarket parts installed as far as i know.all iv done to it is added a 5 in stack out the flat bed.. should i start with the genral and put fuel filters along other normal maintnence? from what iv read on here it should get alot better economy than 10 even if i have a heavy foot, thanks

 

I'd change all fluids,fuel filters, oil,diffs

 

Ok I will try that thanks for the help!

 

I would throw new fluids in it as well... My 91 7.3 IDI got 14-15 miles to the gallon unloaded so I would think your 6.9 should be a hair above 10... Might check brakes and all that jazz as well if you haven't already...

 

need more details on the truck. trans, gears, tire size, mileage?


if you have a c6 trans with 4.10 gears and stock size tires and a worn out fuel system, 10 is what you will get.

 

Tires say 7.5 x16,didn't have a tape measure on me to be exact,it does have a c6 trans and gearing has to be 4.10 or close cuz she gets wound up round 60-65 (judge by sound tach is broken). Motor saposidly has 60k on rebuild as for fuel system I don't know if it's been touched,chasis has 238k on it..I know details are screchy this is all I know rite now. Don't have alot of time to investigate truck between traveling job and family. The help u guys have given me has been a big help,I'm diggin this site! Thanks alot!

 

with the c6,(no overdrive) and the 4.10 gears, at 65 mph you are spining the engine at almost the gov, probly around 3000 rpm. fuel mileage will be hell.

what color are your injectors?

 

I'm not sure,i will look when I get home this weekend. What would be a bad color?

 

grey. if they are grey they are original.

 

Ok thanks alot!