So now that I have the (new to me) ride home, NW Illinois, I spent a day trying to find stations that offer ethanol free 93 octane. The various apps to locate such stations proved largely worthless as most of what they showed as carrying 93 octane were either obsolete or included 93 with ethanol. It seems fewer and fewer stations now carry 93 octane.

I did find two stations, one 30 minutes away and another 40 minutes away, and whenever I'm in Dubuque IA I can run by either, but my question is, has anyone used octane boostsers? Is this a viable option when I can't find 93 octane? I know it'll run on 91, but I'd rather feed it what it wants.

 

So I did find an old thread here on the subject. It doesn't seem there's such a thing as a "good" octane booster additive. 91 octane when I have to, and 93 when I can.

 

Yeah I believe that's the consensus. I learned something interesting about engine additives recently. Apparently the profit margin or markup for petrol at the pump is very thin. Conversely, and I cannot confirm this but the source was legit, markups on additives are extremely high. Make of that what you will. It probably explains the massive marketing around the big oil additive packs in their fuels and oil. I'm in NC and I can get ethanol free 93, so my car is tuned for it. If I move somewhere that has noticeably different fuel, I guess I'll need a different tune. Ideally anyway...

 

I just put Costco fuel in my car and don’t think much about it. I even use this fuel for the track.

 

91 or 93 octane?

 

93, but it’s probably 10% ethanol minimum.

 

Isn't any ethanol supposed to be a big no-no?

 

All normal gas has up to 10% ethanol unless you specifically buy ethanol free gas. Is no-ethanol better? Probably, but it doesn't really tend to cause issues on newer cars (80s+ with EFI), especially if you drive them moderately often. They wreak havoc on carbs if you let ethanol fuel sit in the bowl without running for a long time though. Octane is far more important than ethanol percentage within the 10% legal limit. I wouldn't stress about 91 vs 93 though. These cars aren't turbo'd running aggressive tunes or anything. They are moderate compression NA engines that were sold all across the US including the West Coast where 93 is virtually impossible to find and there are plenty still on the road out there. I put about 5K miles on mine with 91 and never once heard any pinging/knocking even during spirited driving.

 

consider all the high performance and classic Porsches running around California on E15 91.

the UK govt operates this website to tell you if E10 is safe for your car if you're curious about their opinion
https://www.gov.uk/check-vehicle-e10-petrol
(Edit: I'll just post what they say about Porsche here: "E10 petrol is cleared for use in Porsche vehicles with petrol engines since the 1998 model year and all Boxster models with petrol engines since the 1997 model year. The Carrera GT is not cleared for use with E10 petrol.")

I live in California and I go to shell for E10 91 as it's the best I can get. If I could get E10 93 I'd use that instead.

What ethanol really killed is the carburetor.

 

Interesting. Given the option between 93 with ethanol or 91 without, what would you chose?

 

Gas here in Illinois has had ethanol in it for quite some time. Maybe decades. Can’t really do much about it.

 

I would probably do the ethonal free but i cant get that by me so i have been putting ethanol 93 in the car for 4 years now without issue.

 

Definitely 93. It will probably be cheaper and like I said octane is more important and 93 is technically what Porsche calls for. If I was going to let my car sit for an extend period of time I might opt for ethanol free though. All of the issues associated with ethanol damaging fuel components is from extended sitting and manly on carbureted cars.

 

I would probably do the 93 E10 myself as well, but an interesting question. Not sure.

 

So 93E through the driving season, 91 free during winter storage?