I thought I'd start a fuel mileage thread for my 4BT swap, in planning for this swap I read a lot of claims of increased fuel mileage ranging from 17-30+ mpg. The 17 is very believable, older rotary pump motor and keeping the skinny pedal smashed would get you there. 30+ is likely fantasy unless you put the 4BT into a 2wd Ranger, which is done quite frequently for those folks looking to hyper mile it.
I was looking for 20+ with mixed driving, my truck is rolling 35's w/ 4.10's and if I keep it at 65mph it's in the 4BT's sweet spot of 1800 rpm. My first drive was so
that I didn't keep track of mileage, I was just trying to see in the 60 mph rain! For my 2nd and 3rd tank I've kept better track of the numbers. I'll add to this thread as I drive it more and do a few mods to the motor, I'll also try to be descriptive of the driving and atmospheric conditions. 2nd tank: 19.2 mpg. City & hi way driving from Parker to Golden, run up I-70 @ 70 mph with camping gear & supplies for 3 people to Idaho Springs, ran Barbour Fork at 10 am. Gassed in Parker & Idaho Springs, temps ranged from 90 degrees in the metro area to 65 degrees in the mountains.
3rd tank: 20.5 mpg. Around Parker & two runs up to Northglenn, in town driving was at 40 mph & I-25 N was at 65 mph (sweet spot), gassed in Parker. Temps were between 80-100 degrees, almost no traffic and no intentional turbo kick. You can drive it hard and force the turbo to light early and make it maintain it if you want.
4th tank: TBD
