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I've been running Shell 91 for years under the assumption that no Ethanol was the way to go. Was at auto show a couple weeks back and a engine shop told me they tune all their engines for 94. 94 here is premium with ethanol added. He's seen cars come in for a dyno that have serious knock retard and they drain out the Shell , replace with petro 94 and the ECU puts all the timing back. It blew my mind but he obviously knows what he's talking about since thats their business and they have all the equipment to monitor these things. I've read on Diablo forums that they recommend we stay away from "top tier" gasolines due to all the cleaning additives. What are you guys running for higher octane fuels around here? I'm gonna try Petro Can 94 and data log my KR with my tune by Johan. Other than that i have the standard bolt ons that i think everyone started with. CAI , stat, intune, corsa, catch can. I guess its as simple as putting in a tank from each station and monitor KR at WOT after about a half tank and see which my car likes best.
Thanks in advance
 

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I was always under the assumption that it's better to use the shell 91 no ethanol than to use the 94 Petro with it. You may get a little les power but I have read ethanol damages seals and rubber parts over time.
 

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I can vouch for petro 94. Although it uses ethanol it is a better gasoline for preventing knock. I have 6.1 Srt and it knocks less on the 94 than the shell 91.
 

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All our premium gas here has "up to 10% Ethanol". I got more KR with Shell 93 than any other 93 octane gas. BP gives the least KR in my stock 6.1.
We do have 90 octane pure gas and I use it all the power equipment but it was horrible in the 6.1.
 

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So far my research shows that for the best performance use Petro 94 with the ethanol, as ethanol is a better at knock suppression. However your gas mileage will drop 10% which is around 2 mpg. Shell 91 is a "no ethanol" gasoline and will give the best gas mileage.

Let your priorities be your guide.
 
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