I did a search, but none of the ethanol threads addressed whether or not 10% blended gas raises the octane beyond the advertised 87, 89, 93. 10% is a meaningful amount, and would raise 87 to an 89 assuming my math is correct.

I doubt that the ethanol is blended with an even lower octane gas, as there are still markets for non oxygenated fuels. Anyone know the story on this?

 

My understanding (and it could be wrong) is that a 10% ethanol blend has a total octane of what is advertised. So in the case assuming your math was right and 87 octane + 10% ethanol becomes 89 octane.. they would advertise the product as 89 octane.

 

That's the question as 100% ethanol is around 110 octane. How can you take 87 octane fuel, mix 10% ethanol in it (110 octane) and still get 87 octane? It would seem that they would be using a cheaper lower octane fuel to do the blending with for the lowest octane level. I know that when I was in Iowa a few weeks ago, regular 87 octane was without ethanol as far as I could tell but 89 octane did contain it. It was also cheaper than the 87! What brillo's number suggests is that up there maybe all they do is to mix in ethanol with 87 octane to get 89. What about down here in Houston? All of our gas is supposed to contain 10% ethanol now but we still have 87 octane. Is it actually higher than 87 or are we getting lower octane gas than normal and than having ethanol added to it?

 

At first most fuels were getting 1-2 points higher octane after adding ethanol. Some of them have begun to change formulation to lower octane to let the alcohol balance out to advertsised octane. Exxon was the first, and BP should now be at advertised level. Phillips is not likely to change the gasoline stock so it should be 1-2 points higher then advertised.

Two of the higher octane compounds also have higher vapor pressure, as does alcohol. Should the EPA push the Ried Vapor Pressure specs a little tighter on gasohol (currently there is some leniency) then it would almost certainly drop the octane to where the refiners are just meeting the octane.

So far I've been running mostly Phillips. Strange thing is if I buy discount gas I seem to get discounted fuel mileage. Maybe it's me, maybe it's the fuel.

If you want a little extra grunt order a mini-keg of Phillips TT105 and add about 7% methanol. TT105 sells for about $6/gallon, and it will take about 4- 5 gallons to the ECU to "learn" the fuel. You'll get about 4% oxygenation in the fuel which in turn amounts to about 8% more fuel energy potential. Add to that the TT105 cools the air much better (during vaporization) adding another 3-4%. In effect you may see up to 30 more HP. Its not unusal to see 15-17% net gain on the dyno with the 2 strokes we ran on our karts compared to pump fuel.

Ive tried the ealier Phillips blend P-42 mostly because I had some leftover. I didn't bother to mix any methanol to it, but the performance improvement was definately very noticable.