Thrdlife

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

Arctic2002ss

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.

RPM WS6

iTrader: (3)

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.

Arctic2002ss

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

Thrdlife

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

RPM WS6

iTrader: (3)

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.

murphinator

iTrader: (2)

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

NC01TA

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

redtan

iTrader: (5)

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.

amfs1950f-1

Ok so bring this thread back from the dead for a final answer. What it sounds like your saying to me is... Even though our engines weren't designed to use ethanol. Its better to use the proper octane rating instead of a ethanol-free gas. If your going to tune the PCM you can tune it to any octane, but you wouldn't want to change octanes without changing the tune. does this seem correct?

redtan

iTrader: (5)

That's 100% true. Your engine doesn't really care what % ethanol is in there, but octane is king especially in performance cars.

I mean look at all the people running E85. Sure it has 85% (or something like that) ethanol, but it's octane rating of 105 or whatever is what matters for these types of cars.

RPM WS6

iTrader: (3)

That's not really the case. While it's true that LS1s weren't originally designed to use *high* percentage blends of ethanol such as E85 (85% ethanol), lower percentage blends (such as E10) have been available long before the LS1 was introduced - and E10 is fine to use in any LS1.

RevGTO

iTrader: (12)

This is the truth and not the myth that "the higher the octane, the more power". I get KR in certain parts of the powerband, and watched my car go progressively slower as I boosted up the octane with toluene at the track.

Remember, the label at the pump only guarantees the minimum octane level of that gas. Thus the 90 could actually be 91 or higher. And one point of pump octane might not make much of difference on a given car. I would try the 90 no ethanol - if it causes detonation, stop. But it might move the car closer to the minimum "lowest octane with no detonation" sweet spot with the added power production of 100% gasoline.

NC01TA

Since I last posted about 4 years ago, I am now on the verge of losing that 93 no ethanol gas that I have enjoyed. They are switching to 90 octane. My car knocks with anything under 91 so I have to start going to the 93 with 10% ethanol. Not the end of the world, as I have to do that on the road trips we take, but it sure was nice to have real gas.

swathdiver

And after you switched over for daily driving, how did that affect your gas mileage? For everyday driving that is the most important comparison we can make between the two. Yes, I realize the fellow I'm addressing posted over two years ago.

NC01TA

I'm still here. I've used the 93 with ethanol since I lost my other option. I have found the mpg to be slightly worse now. No big deal, maybe 1 or 2 mpg. That's my easy driving style anyway. I do use the Lucas ethanol treatment (3 oz per fill-up) just for grins. I use it in my C6 too. Certainly no harm, and if it helps in any way whatsoever, it's worth it.

swathdiver

Thanks. My motor is tuned for 93 and can run E85 so I switch back and forth but when range is wanted I'd like the best mileage possible. There are E0 90 octane stations around but no E0 91+ closer than 50 miles. I save almost a nickel a mile running E85 but would not be practical on long trips when stations are sparse to non-existent.

99 Black Bird T/A

iTrader: (4)

FWIW on gas mileage...

When 93 with no ethanol was common, I frequently could get 32-34 mpg on the highway in my 91 RS. When the 10% ethanol became common, the mpg dropped 1-2 mpg on average on the same interstate trips. The mpg would return to 32-34 mpg when 93 with no ethanol was available.

With heads & cam, 4.10's my 99 TA could get 26.5 to 27.5 mpg on the interstate on 93 without ethanol. Gas mileage would typically drop to 25.5 to 26.5 mpg with the ethanol blended 93. The mpg would return when ethanol free 93 was available. The cars mail order tune was for 93 octane gas and ethanol wasn't common in 2002.

My 91 RS with the 383 LS1 & 4.10's typically gets 24 to 24.5 mpg on the highway using 93 with ethanol. Without 25 to 25.8 mpg. There seems to be slightly less variance in mpg between the two. The tune was done on 93 with 10 percent ethanol but the car still gets better mpg on ethanol free 93.

WhiteBird00

iTrader: (4)

That's right around where it should be. Ethanol has about 33% less energy by volume than gasoline so the common E10 blend will get 3% to 3.5% lower mileage than the equivalent octane pure gasoline.