So I asked people about their off-road fuel economy, both here at O&E and elsewhere on the internet, tracking down specific vehicle forums and youtube channels. The results are interesting and pretty much exactly as I expected.
My goal was to see what effect engine type had on fuel economy. I think we all generally agree that Turbo gas engines will do great on the EPA cycle but have the potential to do MUCH worse in real life, where NA engines tend to get as advertised and turbodiesel seems to do much better.
Well, it’s pretty much the same off-road as well.
The average percentage of EPA listed city mileage is listed below for each type. Keep in mind these are self-reported and the sample size isn’t huge so scientastic it aint.
NA engines tend to average around 75% of their EPA listed city mileage being used off-road. 78% if you take out extreme outliers. NA seems to be load linear, where more load results in a predictable consumption curve.
Turbo gas engines tend to average around 60% of their EPA listed city mileage being used off-road. I guess the real data here is less that they are less efficient engines, but more than their city mileage targets aren’t realistic unless you can stay out of boost completely. However, I found that the two overland Ranger samples reported worse off-road mileage than the Tacoma and Frontier samples with similar mods done.
Turbodiesel engines tend to average around 93% of their reported city mileage, and they seem to fair the best, though my sample size is smallest here and both are an older type without after treatment. I wasn’t able to find good details on modern diesels like the 28 and 3 liters from GM and FCA. If you have one of these I really want to know what you get off-road both in high range and low range if you have it.