I bought my 93 7.3 IDI 4x4 F250 (ext cab, full size bed, no turbo, 285/75R16 AT tires) a couple years ago and got 19.5 mpg on the way home keeping at 55 mph (~75 mile or so IIRC). Then I had a new IP and injectors installed (at very reputable diesel shop) and have never got that mpg again. Mechanic said he "turned up the pump just a little", but I'm not sure that has much to do with it.
But my MPG seems to be all over the map, but I don't check it unless I'm on a little road trip. Track miles with GPS since PSOM is shot (no speedo or odo). I just fill up the tank till I see diesel in the fill neck. Then when I get back, I fill it up the same way. I always keep both tanks completely full. Use Power Service Diesel Clean in it. Truck does not have a tailgate. I usually drive with all the windows open unless its raining or too cold.
I recently drove 100 mi round trip to pick up feed. Drove back with ~2000 lb in the bed and got 15.4 mpg. Not too bad.
Then, I drove about 150 miles round trip (in heavy rain most of the time) and only got 12.5 mpg.
One difference was that on the first 100 mile trip, I did my best to keep it under 55 mph (using GPS speedometer app on my phone). The second 150 mile trip I wasn't as particular about keeping 55 or under, but I did drive kinda slow because of the rain -- sometimes 35 mph, sometime fast because the rain slacked up.
I think once you get over 55 mph, your mpg goes downhill fast.
But my MPG seems to be all over the map, but I don't check it unless I'm on a little road trip. Track miles with GPS since PSOM is shot (no speedo or odo). I just fill up the tank till I see diesel in the fill neck. Then when I get back, I fill it up the same way. I always keep both tanks completely full. Use Power Service Diesel Clean in it. Truck does not have a tailgate. I usually drive with all the windows open unless its raining or too cold.
I recently drove 100 mi round trip to pick up feed. Drove back with ~2000 lb in the bed and got 15.4 mpg. Not too bad.
Then, I drove about 150 miles round trip (in heavy rain most of the time) and only got 12.5 mpg.
One difference was that on the first 100 mile trip, I did my best to keep it under 55 mph (using GPS speedometer app on my phone). The second 150 mile trip I wasn't as particular about keeping 55 or under, but I did drive kinda slow because of the rain -- sometimes 35 mph, sometime fast because the rain slacked up.
I think once you get over 55 mph, your mpg goes downhill fast.
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