I have a 85 6.9 idi 4x4 single cab long box with 3.55 gears and 4speed manuel no O/D. What should I be getting for mileage? Its hard for me to know because my fuel gage barely works.

 

Give yourself about 13 mpg mixed, should be a little higher but safe>sorry. Fill the tank drive for about 150 miles and refill. Record miles from the trip/odo and divide by gallons it took to fill it.

 

I got like 12 in my crew cab with the 6.9, 4x4, and the 4 speed. Like 10 with my 11 foot camper on the back.....

motor is totally clapped out btw.

 

i pulled 21 out of mine on highway with 35 inch tires and 355 gears also had a 4 speed np435

 

My 1986 F350 4x4 crew cab 4 speed with 4.10's and a gear vendor's overdrive unit got 17 mpg almost no matter what. The final drive ratio with the GVOD is 3.20 so just a little more than your 3.55's. With the GVOD off in straight 4.10 final drive ratio it got 15 mpg. Fairly fresh engine and IP and injectors. Wear on the fuel system and timing makes a big difference.

 

88 F250 single cab 2wd 3.55 gears and C6 is getting 18 around "town". Around 15 @ 70, dad said he was getting 17 @ 60, i dont have that kind of patience lol

 

i never go faster then 55mph

 

can I have a picture.

 

2-7-16 his last appearance.
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Charlie