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Discussion Starter #1
I’m soon to get a 987.1 cayman 2.7L, and I’m wondering if the car would be more fuel efficient if I use 93 or 91. The previous owner always used 93, so would there be an issue if I tried using 91?
 

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There's no difference in fuel economy between any of the differrnt octane fuels. There is, however, a difference In maximum power available if the engine is tuned to take advantage of the higher octane.

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An engine tuned for higher octane can operate with higher compression since the octane rating is a measure of the compression the fuel can withstand without pre-igniting. However, the octane rating has nothing to do with energy content so your gas mileage shouldn't change between 91 and 93.

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Discussion Starter #4
There's no difference in fuel economy between any of the differrnt octane fuels. There is, however, a difference In maximum power available if the engine is tuned to take advantage of the higher octane.

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Is the power difference noticeable at all?
 

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Yes, as I said, "if the engine is tuned to take advantage of the higher octane." Mostly, this performance difference will be apparent under conditions of maximum load. For daily driving, you're not likely to notice a difference.

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Agree, I have a 987.1 cayman 2.7L. The owner's manual recommends 93 but says anything over 90 is ok. The ECU will adjust and the power difference because of that will be negligible. That said, I wouldn't drop to mid-grade or regular.

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Discussion Starter #7
Agree, I have a 987.1 cayman 2.7L. The owner's manual recommends 93 but says anything over 90 is ok. The ECU will adjust and the power difference because of that will be negligible. That said, I wouldn't drop to mid-grade or regular.

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Definitely never going lower than 91. What do you use?
 

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too bad we don't have that choice here in CA, stuck with 91
 

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As others said, 93 is preferred, 91 is acceptable, and I’d add no ethanol is my preference, as is Top Tier rated. I use busy stations so the fuel in their tanks is fresher due to turnover.

Power differential won’t be noticed, unless you use the car at full performance, think 1-3%. Passing in the mountains is where I want it the most.


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too bad we don't have that choice here in CA, stuck with 91
I am lucky to have access to a performance gas station here in Oregon that sells up to 97 octane. It's not cheap though! Close to $4/gallon. So, I use it at the end of the year before I store my Porsche for the winter.
 

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There have been countless studies published over the years that conclude that there is a negligible difference in performance between the various grades of gasoline. All cars sold in the US must function on regular unleaded which is what their EPA performance data is based upon.
 

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While I agree with all the above statements regarding power, my personal experience is somewhat different. Circumstances required that I make multiple cross country (1350 miles) interstate drives in my '09 987.2 2.9l. I experimented with different octanes just for fun.
I found that mileage varied measurably with octane - higher octane, greater mileage, as much as 10% lower mileage with lower octane. I typically ran speed limit +10% and used the cruise control.
Given that the price:eek:ctane ratio was much greater than 10%, the lower octane provided more miles/dollar despite reduced efficiency.
The car demonstrated no perceptible issues as the octane sensor seemed to adapt readily. Old school logic is that once warmed up, the octane is less critical.
Would I run low octane around town on short trips? Absolutely not.
IMO, higher grade fuel is necessary not just because of the octane but because of the beneficial additives that come with it.
When I autoX or track my car, I use the highest octane non-ethanol fuel I can find. I recognize that this runs counter to current logic in that ethanol has more power potential than pure gas but my butt dyno favors the pure gas.
Best to all. Oh - your mileage may vary ...
 
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Luckily we have 93 octane here.. I have a Malone ecu so they do recommend 93 or “higher’r octane“... as he said further up.. on an N/A car unless your at full tilt, 91 minimum I’d say....
 

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I found that mileage varied measurably with octane - higher octane, greater mileage, as much as 10% lower mileage with lower octane.
My experience with our Audi and Cayman S is similar. Both cars give better fuel mileage when using premium than when using mid-range fuel, which in Washington State is usually 89 octane. Better fuel mileage means the engines are operating more efficiently on premium. Because of this, I stick with the manufacturers' recommendations and no longer put anything but premium in them.
 
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