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Discussion Starter · #1 ·
Recently, a gas station that sells non-ethanol gasoline took over the location of another gasoline retailer in my neighborhood. The old retailer did not sell Top Tier gasoline. The new retailer sells Top Tier gasoline. The new retailer also sells non-ethanol Top Tier gasoline, but only in 89 octane. Should I continue using the 92 octane with 10% ethanol or should I switch to the 89 octane non-ethanol gasoline? Both would be Top Tier gasoline. Which would be better for the Cayman?
 

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These cars have around 11:1 compression ratio. I think we need the octane. I also have no problem withe the alcohol. I used E85 in my Vette for 3 years, no problem. It burns very clean.
 

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Fortunately, I don’t have your problem, since my 94 octane is ethanol free. I’d likely use less of the performance in winter when, in my understanding, ethanol attracts condensation moisture. For winter, my preference would be non-ethanol, and use the higher octane in warmer weather.


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Porsche recommends a "octane" (AKI) rating of 93 and no less than 90 (see clip from manual below). I generally use the PetroCan 94, which has ethanol. I have had no issues using it in the winter.

If you use the 89, your engine will retard the timing to prevent knocking, but performance and mileage will suffer somewhat.

Fuel Recommendations

Your Porsche is equipped with catalytic converters and must use UNLEADED FUEL WITHOUT METALLIC ADDITIVES ONLY.
Your engine is designed to provide optimum performance and fuel economy using unleaded premium fuel with an octane rating of
98 RON/ 88 MON (93 CLC or AKI). Porsche therefore recommends the use of these fuels in your vehicle.
Porsche also recognizes that these fuels may not always be available. Be assured that your vehicle will operate properly on unleaded premium fuels with octane numbers of at least 95 RON/
85 MON (90 CLC or AKI), since the engine’s “Electronic OctaneTM knock control” will adapt the ignition timing, if necessary.
 

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These cars are engineered to run on the highest octane you can get at the pump and with ethanol. I would never use less than 93 RON even in my 987 and prefer Top Tier whenever possible.
 

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93 in the 987 with 10% ethanol, usually Top Tier Shell or BP. Everything else runs on 89 non-ethanol. Tried the non-ethanol lower octane on the 987 and the Miata. Not good - don't like it. I'd happily pay for the 93 ethanol free but the corn lobby and the politicians they buy won't let me.
 

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I use ethanol free 91 octane and happy with it. Have tried 94 octane with 10% ethanol, didn't notice performance difference. Ethanol free gas will provide better mileage since ethanol carries less energy
per unit than gasoline. With 10% content this is a small difference but paired with higher cost of 94 octane gas is something to consider. Addition of ethanol is an easy way for gas companies to boost octane (pure ethanol is RON 113).
 

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Fortunately, I don’t have your problem, since my 94 octane is ethanol free. I’d likely use less of the performance in winter when, in my understanding, ethanol attracts condensation moisture. For winter, my preference would be non-ethanol, and use the higher octane in warmer weather.

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Who sells 94 ethanol-free in Alberta? Petro Canada and Husky 94 have (up to) 10% Ethanol...and the only non-ethanol premium I'm aware of is Shell 91. If I could find 94 with no ethanol close to me, I'd drive up to 2o or 25 miles to fill up.
 

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Who sells 94 ethanol-free in Alberta? Petro Canada and Husky 94 have (up to) 10% Ethanol...and the only non-ethanol premium I'm aware of is Shell 91. If I could find 94 with no ethanol close to me, I'd drive up to 2o or 25 miles to fill up.
None listed on the Pure Gas website.

https://www.pure-gas.org/index.jsp?stateprov=AB

Looks like Chevron in BC has ethanol free 94.
 

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Who sells 94 ethanol-free in Alberta? Petro Canada and Husky 94 have (up to) 10% Ethanol...and the only non-ethanol premium I'm aware of is Shell 91. If I could find 94 with no ethanol close to me, I'd drive up to 2o or 25 miles to fill up.
Drive to BC to fill up. Chevron stations here all have top tier 94 octane, ethanol free. My car finds it very tasty.
 

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Drive to BC to fill up. Chevron stations here all have top tier 94 octane, ethanol free. My car finds it very tasty.
Ah...you're wintering in BC, aren't you kmaneh?
 

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Discussion Starter · #13 ·
Fortunately, I don’t have your problem, since my 94 octane is ethanol free. I’d likely use less of the performance in winter when, in my understanding, ethanol attracts condensation moisture. For winter, my preference would be non-ethanol, and use the higher octane in warmer weather.


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Winter is not an issue for me. I'll keep using the Top Tier 92 with 10% ethanol as I have not been able to find any place that sells higher octane to the general public whether it be with or without ethanol.
 

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Recently, a gas station that sells non-ethanol gasoline took over the location of another gasoline retailer in my neighborhood. The old retailer did not sell Top Tier gasoline. The new retailer sells Top Tier gasoline. The new retailer also sells non-ethanol Top Tier gasoline, but only in 89 octane. Should I continue using the 92 octane with 10% ethanol or should I switch to the 89 octane non-ethanol gasoline? Both would be Top Tier gasoline. Which would be better for the Cayman?
Octane does not "boost" performance; it simply makes combustion happen at a higher temperature. When you compress a fluid (like fuel), it makes it hotter--just physics. The engines in Caymans have an 11:1 compression ratio--higher than a "normal" engine. That is the reason they require the higher octane.

So, the ONLY reason to use 93 octane is if you need to to prevent early (before the spark) combustion. Early combustion can cause damage to your engine! That said, many newer cars, like Caymans, will automatically advance the timing, when using 89 octane, to prevent damage, but the cost is in performance due to the fact that the timing is not optimal.

On the flip side, if you have a Honda Civic, 93 octane will do NOTHING (except cost you more money) because the engine has a lower compression ratio.

And as a previous reply said, ethanol gives you a little worse gas milage because it has less carbon in it, but newer cars are made for it. Octane and ethanol are two completely different things--not even comparable.

If you want LESS performance in your SPORTS CAR and nominally better gas milage, use the 89 octane, ethenol-free. Otherwise, stick with the 93 octane, 10% ethenol.
 

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So, the ONLY reason to use 93 octane is if you need to to prevent early (before the spark) combustion. Early combustion can cause damage to your engine! That said, many newer cars, like Caymans, will automatically advance the timing, when using 89 octane, to prevent damage, but the cost is in performance due to the fact that the timing is not optimal.
Timing is retarded to reduce spark knock from low octane, not advanced.:cheers:
 

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Didn't see any voting buttons, but I'm voting for 92/93 octane, every time. Unless you are driving in freezing temperatures. You will get more power from 92/93 octane. At frigid temperatures, all bets are off. Traction might be the bigger issue...
 

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If you're just driving around in traffic or cruising on the interstate you're fine with anything coming out of the pump. If you ask the engine for performance - octane matters. More important than what the pump says is how long the fuel has been sitting in the tank at the station. Fresh 89 will give you less problems than 3 week old 92...
 

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If you're just driving around in traffic or cruising on the interstate you're fine with anything coming out of the pump. If you ask the engine for performance - octane matters. More important than what the pump says is how long the fuel has been sitting in the tank at the station. Fresh 89 will give you less problems than 3 week old 92...
Again, high octane does not increase performance unless your engine is designed for it (i.e. High compression ratio).

And, if your car is an older model, and designed for high octane, you can severely damage your engine by NOT using enough octane.
 
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