Interesting Fuel Economy data

"HammerheadFistpunch" (hammerheadfistpunch) 07/28/2020 at 18:49 • Filed to: None

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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 t urbodiesel 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.

ITA97, now with more Jag @ opposite-lock.com > HammerheadFistpunch 07/28/2020 at 19:02

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I, too, would curious what any of the smaller, modern direct injection diesels get tooling around off-road. The similarities to my small, antique mechanically- injected turbo diesel pretty much begin and end at the fact the burn the same fuel and not really much else.

HammerheadFistpunch > ITA97, now with more Jag @ opposite-lock.com 07/28/2020 at 19:06

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yeah, you and MtDrift were the only ones with diesel input and his was the same story, in fact he reported 100% basically.  Granted I think 90% is realistic even with a modern diesel unless its in regen a lot.

BaconSandwich is tasty. > HammerheadFistpunch 07/28/2020 at 20:21

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Interesting. I actually would have expected worse fuel economy numbers.

If only EssExTee could be so grossly incandescent > HammerheadFistpunch 07/28/2020 at 20:30

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The tuning that makes turbo engines work well (lower compression and retarded timing) makes them less powerful than NA when you’re off boost. Unless you have a setup made specifically to give power  at low RPM, like a turbodiesel, it makes sense that fuel consumption would be worse cause you have to give it more beans.

Did you make any distinction between new and old turbos? I’d imagine the newest engines would fare better since they can adjust timing and stuff to compensate while off boost.

I’m also curious to see how superchargers fare offroad.

Rusty Vandura - www.tinyurl.com/keepoppo > HammerheadFistpunch 07/28/2020 at 20:32

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I got 15 mph towing my tent trailer across Nevada. I always get that mpg with that trailer behind the Safari, even with the entire family and more suitcases.

We made the round trip between the Bay Area and Logan for grandchild and I thought of you frequently because you recommended the Carlisle trailer radials that made such a YUUUUUGE  difference in ride quality.

SBA Thanks You For All The Fish > HammerheadFistpunch 07/28/2020 at 20:36

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Thanks. Great data.

Yeah, I always hear the EcoBoost Apologists with “oh, it will hit the numbers if you keep it out of boost...”. Why bother if the efficiency goes to crap if you actually drive it the way it was meant to be driven.

OTOH, I think the modern DoD and VVT engines do a pretty good job mapping  to their promises.

HammerheadFistpunch > If only EssExTee could be so grossly incandescent 07/28/2020 at 21:06

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2 modern turbos and 1 supercharged. The supercharged one did terrible

If only EssExTee could be so grossly incandescent > HammerheadFistpunch 07/28/2020 at 21:12

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I bet it did. Superchargers are terrible for just about everything but making noise.

CRider > HammerheadFistpunch 07/28/2020 at 22:17

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What’s this “fuel economy” thing you’re talking about?