Remembered from a Los Angeles Auto show visit seeing the gas cap area on the Porsche’s show the 93 (AKI) octane label, I was reminded of this after my wife put a deposit on a ‘13 GTS. Sure enough, an online manual notes this as a “recommendation”, that the car knock sensor will adjust timing to compensate for fuel of at least 90 (AKI) octane.

If my math is correct I can mix 3 gallons of readily available 91 with 1 gallon 100 Racing fuel to get roughly 93 (93.25 my calculations say). Is all this effort, (and cost), advisable? (The 100 octane is usually right under $10/gallon, and I’ve got to drive about 15 mi one way to get it).

Any thoughts/experiences appreciated! Thank you.

 

Sounds like a lot of hassle for negligible benefit. Hell, you'll burn almost 2 gal just goin' and gettin'. If it were a Turbo with a very aggressive tune... maybe? But hard to imagine a normally aspirated motor benefiting with just a minor bump in octane. Just my 2-cents.

 

I appreciate your thoughts! Thanks!!!

I showed my son this thread and his thought was to take our other much more fuel efficient car to get the 100 octane. (I noted I have a 5 and 2 gallon gas container that could be used for holding it).

I'm not a fast driver, in particular since my June 1st at fault wreck. So I may not even need high output from the engine, at least for a while...

 

I lived in NorCal (Silicon Valleya area), and never saw higher than 91 octane. Seems CA is banning anything higher. No worries now though, not living there anymore.

 

When I started driving there were two places around me that I knew of that sold 100 octane fuel. One was in a ritzy neighborhood called San Marino, the other is the place that I know of that still has it in West Covina, just south of the 10 FWY Citrus Ave exit, a 76 Station. It catches your attention because the price is $9.xx per gallon! In more recent years my wife accidentally put midgrade in a '92 190E and I went with my portable container to get some to slowly add and protect/baby that old engine. I noticed a very unique aroma to it, well, actually, no smell at all. As I understand sulfur (in PPM) is added to fuel to give us the unique warning smell that it's around. This stuff had absolutely no smell at all, (not that I'm interested in sniffing fuel, but I just noticed as I was filling the container.)

There's supposedly a place in Irwindale near the Speedway that has it, but whenever I drive by I don't see a station that is readily accessible to the public. (I don't see a station from the street that is, never been inside.)

(Actually, I haven't been to the 76 station in a while, so I better go check if they still sell it! )

 

Why? Retarded timing better for emissions because generates less NOX from the lower combustion temperature? Seems like it would have a minor impact.

 

Under "Operating Your Porsche in other Countries: ... In some countries the available fuel quality may not meet requirements and can result in coking around the intake valve. In this case, the fuel may be mixed with the additive sold and recommended by Porsche after consulting an authorized Porsche dealer. Porsche part number 000 043 206 89.
-> Observe the instructions and mixture ratios stated on the container.
It is important that the service intervals, particularly the oil change intervals, are observed in accordance with the specifications in the "Maintenance" booklet."

 

I can safely say, there is no noticeable effects at all. In anaheim, we have a 76 station that has 100 octane on pump and usually hovers around $10-12/gal. Ive even filled up the entire panamera tank with 100 0ctane with very slight HP increase, however, the gas burns through MUCH quicker, haha.

 

From the manual excerpt, it seems our coked intake valves may be, at least partially due to using relatively poor 91 Octane fuel. I stopped by the 76 (on the way home from visiting IKEA) to fill the 5 gallon container with racing fuel, but the 100 octane label was missing/removed. I now have 7 gallons, enough to make the 93, so long as the fuel I bought I is still 100 octane.

That’s a huge investment in gas to fill it with pure 100 octane fuel since the Panamera tank is so large! I tried it in an ‘09 C350 and engine seemed smoother. I tried it in a ‘10 CTS-V and felt no improvement. I guess it depends on the engine...

 

since the fuel never touches the valves (direct injection) I can't see how the quality of the fuel can effect the coking on the valves - the cylinders yes, the valves no.

 

This is my initial understanding as well, but my quote seems to note how imperative fuel quality and on time oil change/service can be preventative. (That's why I quoted the text from the manual).

 

I have never understood this line of thought. Carbon deposits (coking) on the valves is a result of the combustion process, ie burning the fuel and to a much lessor extent buring the engine oil. It makes perfect sense different fuel formulations can result in different depositing throughout the combustion chamber, valves, and downstream through the exhaust system (turbos, etc). Just because unburned fuel does not wash the intake valves does not mean that the fuel formulation does not impact carbon deposits throughout the engine, including the intake valves.

 

my bad, generally when most talk about carbon build up they are talking about the build up on the intake side of the valves, were no fuel is ever seen on direct injection cars.
now if you're talking about build up in the cylinder side, then yes, fuel quality and additives can help.

 

I had been getting roughly 50/50 100/91 octane until my wife complained about the large refueling bills. (Per octane calculator, right around 95 octane AKI). So I leaned it out to right around 93 by doing 3.25 gallons 100 and 14 gallons 91. Strangely, (or not)?, the engine runs noticeably smoother with 93 than with the 95. Hmmm. Anyone knows what’s going on? Less aggressive timing maybe?