What effect does the addition of ethanol into the fuel have on mileage - especially on the Mini S?

In the late 1990's, when ethanol was forced on us only in the winter, I noticed my Toyota truck's mileage decreased by about 8%.

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Generally lowers gas mileage but do not overdo it. We still have ethanol gas in the winter in many areas.

 

I'm NOT adding it - I hate the stuff!

 

More ethanol = less MPG. Sucks. I'd rather be eating or drinking that corn than burning it in my car. Oh well.

 

Ethanol has about 34% less energy than gasoline on a volume basis, so an E10 blend (10% ethanol, 90% gasoline) should reduce mileage about 3%. Tests under controlled conditions have confirmed that this is approximately the average loss in mileage. Many people report much greater mileage losses, but I'm skeptical of most of them mainly due to the number of confounding factors involved.

- Mark

 

You know, it may in fact decrease mpg, but the MINI's mpg is so sensitive to speed and driving style that ethanol may not be worth discussing.

I've found that if I am gentle in driving style, I can get the OBC into the high 43 to low 44mpg range. Even with the 2.5 mpg optimism of the OBC, that's still over 40mpg. If I don't shift early and accelerate gently, I can drop that to 37 or 38.

Likewise, if I run an indicated 70mph (approx 65 mph true), I get about three to four mpg more than if I run 80mph indicated.

Would like to know how ethanol stacks up to these numbers. Not saying I like e10, but not sure we can't overwhelm it with our speed and style.

 

Less energy content or BTU's per gallon/pound. The net result is lower MPG, but it has been used as an additive in some brands of upper grades of auto fuel for years as an octane improver. When they mandated the use of blends, it caused a lot of problems for fuel users as the blends cleaned out the stations tank by putting the gunk into users tanks....remember the spike of both mini and BMW fuel pump failures about 4 years ago, and if you paid attention a lot of temporary gas station closures as the stations cleaned their tanks!!

 

Here in CA, we get the wonder-stuff all year 'round. Yay (NOT!) "We" tried MTBE for a bit, and found that did really bad things for ground water (wells). So, we switched to alcohol, too. It was mentioned before that ethanol has a great octane equivalent, something like 160. Never knock. But the energy content makes for lousy mileage, as mentioned.

Speaking of octane numbers, our premium, at least in the LA area is 91 (average of motor and research). Do we have octane envy? Yeah, maybe.

 

Gee whiz...first I find that my new mini's fuel gauge isn't even close to the "actual" amount in the tank, now you're saying the speedometer is not correct. Sheesh, I guess I'll have to clock it to see where mine stands!

I'm not sure about the fuel consumption value either... yesterday I was going down the western side of Vail pass in Colorado and the darn thing was reading 92 mpg. On trips (consistent Interstate driving) the OBC will read around 45 mpg but the actual calculated value is 38.

What's the problem with BMW - don't they know how to make accurate measuring devices?

 

Well, they renound renowned for claiming lower than actual HP for their engines.

Many cars have speedometers that claim faster than actual mph. However, the odometer is a different matter. I believe it is much more accurate than the speedometer (unless you put the wrong dia. tires on the car).

Although the MINI's fuel gauge is more extreme than most, I've never had a car with one that was acurate.

IIRC, using more gas with more than 10% ethanol can cause problems with 2nd Generation MINIs (not sure about 1st Gen.), is not recommended by MINI, and could void the warranty.

 

Ugh here in Florida it seems all we can get is the E10 blend, It must be law here as nowhere can I find fuel without ethanol.
Took a BMW 328ci up to Tennessee this spring (got to love the dragons back) and found real 100% gas if I remember right the car did 3 to 4 MPG better then with the blend.

JohnNJohn

 

As Markjenn put it, E10 should *theoretically* reduce mpg by about 3%.

Real world seems to show a much higher difference, around 10% or more. I imagine that ethanol, as it has a lower burning temperature, would have a dampening affect on gasoline. Add on top of that ethanol absorbs water easily and it only makes things worse.

 

NH once used MTBE...same groundwater problems as noted in CA, so now E-10 is the standard.

 

Again, "real world" is mostly anecdotal reports from users who don't gather enough data under controlled conditions and/or are looking for a boogeyman to blame. There have been MANY runs on dynos with E10 and the actual measured fuel efficiency drop is just what is predicted - about 3%. There is no "dampening effect". I'm not saying that there aren't outlyers where certain engines in certain cars in certain situations do much worse (or better for that matter), but all the objective data shows you will probably lose about 3% with E10. Believe otherwise if you like but there isn't really any good data that shows general widespread losses above this nor any technical explanation for losses significantly higher.

- Mark