straight gas vs. 10% ethanol blend

[kit352]

Originally Posted by SpeedKnight

To the O.P., where in the Carolinas were you that you found unspiked gas?!? I'd like to lay hands on some to run in my lawn equipment and my motorcycle. My 1995 VW GTi might benefit, as well.

I saw it all over it seemed but mostly in the charleston area for sure. A couple places in nc had it as well. I just remember cause they were close to ckick-fil-a. Most places had it very clearly displayed at the pumps but others had tanks set back kinda like diesels are.

Im really bumbed about this straight gas thing. it seems to be a clear advantage for some parts of the country and im gonna be stuck on crappy winter blend. maybe i should move to a more mpg friendly part of the country.

[bowtieguy]

Originally Posted by SpeedKnight

To the O.P., where in the Carolinas were you that you found unspiked gas?!?

north...http://pure-gas.org/index.jsp?stateprov=NC
south...http://pure-gas.org/index.jsp?stateprov=SC

[SpeedKnight]

Originally Posted by bowtieguy

north...http://pure-gas.org/index.jsp?stateprov=NC
south...http://pure-gas.org/index.jsp?stateprov=SC

Thanks... I ended up finding that in a different thread after I posted on this one. Turns out I'd spend more getting to the nearest pure gas station than I would ever save by using pure gas. Not to mention, I'm too lazy to drive 21 miles just to get gas for my lawn equipment (which would benefit the most).

[Jay2TheRescue]

21 miles I'd do it just to see what was possible in my vehicle with real gas. Do it once just for science.

[trollbait]

I once came across a little study which compared the fuel economy of differing gasoline/ethanol blends, from pure gas to E85. It was just in 4 unmodified cars; a Toyota, a Ford, a GM, and a GM flexfuel. The expected fuel economy loss as ethanol concentration increases was seen except at 30% to 40%.

At that concentration the GMs were getting the same or slightly worse fuel economy than pure gas. The Ford and Toyota were getting better. The study was too small to draw a real conclusion besides this might something to look into, but energy content isn't the only factor to consider. The differing mixtures will have different viscosities, densities, vapor pressures, etc. As was said earlier, all bets are off if the ethanol changes the engine's efficiency.

Ethanol is also a high octane fuel, 105 IIRC. So tuning an engine that runs on 87 for it isn't going to be able to take full advantage of it. The fact that E85 is mixed with regular, not premium, and flexfuel engines aren't higher compression, is the first sign of the boondoggle the program is.

[GasSavers_Erik]

I agree that an engine could be tuned to run better on higher octane E10 fuel than on E0 gas (one could run more ignition timing advance without preignition), but are you saying that the octane ratings on the pumps are incorrect?

In my area, the E10 and E0 pumps both have the same octane rating listed on the pump in black and yellow numbers (87).

In other words, would 87 Octane E0 resist preignition less than as 87 Octane E10?

[theholycow]

Pumps here are marked with the minimum octane of dispensed fuel. There's no promise that the fuel isn't higher.

However, I doubt that 10% 105 octane ethanol is enough to raise gasoline's octane above 87. I imagine that classic octane boosters are still added just to get it up to 87 from whatever its pure octane rating is.

[GasSavers_Erik]

Good point- since the printed number on the pump is a minimum octane value, then the E10 octane may be higher.

[trollbait]

I'm referring more to the E85 and flex fuel engines. If the powers that be were serious about the flex fuel concept, then the 15% gas in E85 would be premium octane and the engines would have a higher compression. As it is now, it's like calling for premium gas in a regular gas engine.

[theholycow]

Would the rating of the 15% gas matter? How does octane rating dilute? If it's simple math then 85% 105 octane ethanol with 15% 80 octane sub-regular gasoline would still come out to 101.25 octane.