A big discussion point whenever Air-Cooled Porsche owners get together is whether the cars should use ethanol-free gas. The reason is that common wisdom is that Ethanol in gasoline is corrosive and degrades plastic and rubber components of your fuel system and can burn at higher temperatures causing premature cylinder wear and scoring.
The big question now is, should you only use Ethanol-free gas in your Air-Cooled Porsche? The first place to look is to Porsche. According to the Porsche web site, it is suggested that any Porsche prior to 1996 should use Ethanol-free gasoline. From 1996 on-wards, Porsche engines were designed to accommodate ethanol gasoline.
Just the fact that Porsche recommends the use of ethanol-free gasoline for air-cooled Porsches prior to 1996 should be enough to make you fill your Porsche with ethanol-free. The other consideration is that you normally don’t drive your Air-Cooled Porsche on a regular basis so the gas is sitting in the fuel system and has a greater opportunity of causing corrosive damage to your fuel system.
Ethanol started to be added to gasoline in the late-1970’s and most top-tier gas stations now have Ethanol-blended gasoline. A top-tier gasoline is defined as one that maintains levels of detergent additives that result in higher standard of engine cleanliness and performance compared to the EPA requirements.
Locally in North Carolina we are fortunate to have Quality Plus Gasoline stations that offer 93-octane ethanol-free gasoline.
To find solutions in your area for ethanol-free gas stations you can use the web site Pure Gas. http://www.pure-gas.org/
What is unknown about Quality Plus is “Are they a Top Tier Gasoline providing the detergents for added cleanliness to the fuel system?”
Air Brigade member Don went to a Petroleum Engineer friend with this question. Here is a Petroleum Engineer’s response to this question:
If he choses to use Quality Plus non-ethanol, his concern about additives is well founded. Gasoline (premium or regular) coming up the Colonial ( Pipeline)is either "specific" to a shipper (may or may not have an additive, although probably not since it is just as easy to inject it at the terminal) or "fungible" (no high quality additive).
My guess (Petroleum Engineer) is that Quality Plus buys from a fungible wholesaler/shipper so it is anybody's guess as to what the additive package Quality Plus adds after they buy the product. It is interesting to note that the Quality Gas website is silent on the issue of additives.
Given the Porsche recommendation, it seems to me that, absent being able to verify the quality of the Quality Gas additive package, it would be safer to use a name quality premium gasoline. Adding an after market detergent additive also seems risky (what is the right product, what it the right amount to add to the tank, how frequently should he add it, etc.).
As an aside, by far and away the best price for high quality premium gasoline is at Costco (from an independent web site: Costco is a licensed TOP TIER brand that sells its own formulation of Kirkland Signature Gasoline, which contains five times the deposit control additives required by the EPA). By my experience, their premium prices are from 50 to 90 cents per gallon lower that the majors.
Air Brigade has reached out to Quality Plus with the question about what detergents are added to their gasoline, but have yet to receive a response.
Air Brigade will continue to use Quality Plus for their 1968 911 and 1986 Carrera 3.2. Per Porsche recommendations, Shell ethanol premium gasoline will be used in the more modern 2009 911 Turbo. According to the Pure Gas web site, there are other options from Top Tier Gas Suppliers that offer ethanol-free gasoline and these will be checked out to see it that is the case.
Look for similar options in your city at Pure-Gas.org
Running Ethanol in pre-1996 cars is not recommended by Porsche as noted in their web site https://www.porsche.com/uk/aboutporsche/pressreleases/pcgb/?lang=none&pool=uk&id=2011-05-23-classic