General LSX Automobile Discussion - 90 octane non ethanol vs. 93 octane w/ethanol ?

I searched the forum and no one ever gave a straight forward answer to this.

The thing is that Ethanol will raise the octane of the fuel but it is has less energy so you use more fuel. With 90, the computer may switch to the low octane table and cut your power and use more fuel. These cars (assuming you have an LSx) just don't run as well on the low octane table so run the 93 whether it has ethanol or not. At least that's the way I understand it.

Hmmm, that brings up the question of how ethanol in 90 octane would work?

BTW, I have ran E85 in my 2010 Silverado and the loss in mileage cancels out the lower (subsidized) price.

What is the straight answer you are looking for? I didn't see a question?

93 octane will be more resistant to detonation than 90 octane.

Fuel containing ethanol will produce less MPG than fuel without it.

These two fuels are not directly comparable nor interchangeble because they are not the same octane rating.

These two fuels are not directly comparable nor interchangeble because they are not the same octane rating.

Yet somebody still had the bright idea to mix them......:eyes:

The question is will you make more power on an ls1 with 93 gas W/ethanol or 90 octane w/o

The question is will you make more power on an ls1 with 93 gas W/ethanol or 90 octane w/o

You will always make the most power by using the lowest octane possibile that still 100% resists detonation in a given application. A stock LS1 calls for at least 91 octane for best results, anything less and you may see some KR (knock retard) due to detonation. With enough KR, the PCM may move to the low octane spark table, further reducing power, until reset. Any time you see KR, you are losing horsepower.

I'm not sure why you are comparing ethanol 93 vs. non-ethanol 90. Any performance comparasions should always be made at the same octane, otherwise you are introducing an additional variable, thus rendering the results inconclusive. A good experiment will only change one variable at a time. Test E10 93 vs straight 93 for meaningful results.

agree with above ^ go with the 93.

I have done some experimenting with blending e85 with pump premium on another platform and when you up the concentrations of ethanol further is where it really starts to shine over gasoline with its additional charge cooling and detonation resistance , great for boost or high compression.

indy cars run close to 19 to 1 comression on e98 , gasoline is simply not capable of that , ethanol is a better fuel as far as producing power but at 10% its really not going to do anything for you if the octane were the same

Fortunately I have 93 'no ethanol' in my area but if they dropped it for 90 octane 'no ethanol', NO WAY would I put that 90 in my LS1. Octane is still the most important.
For those that missed previous threads, here is the link to see if 'no ethanol' is sold in your area. www.pure-gas.org

The question is will you make more power on an ls1 with 93 gas W/ethanol or 90 octane w/o

Not only does the 93 gas have more octane rating, it has some ethanol in it which helps with the cooling effect. It's 93 with ethanol by a long shot.

This is of course if you tune each fuel to its max potential. If you just dump either fuel in your tank with the stock tune, you probably wouldn't notice any power difference. But if you went all out on the tune for each fuel, the 93 octane will take more timing and make more power.