VLJ

I had a tune on my WRX back in the day and remember paging through the COBB Accessport files and there was a program called ACN 91 which stood for Arizona, California, Nevada 91 octane. Apparently we all share the same garbo fuel.

GrantG

Yeah, we only have 91 here too (ok for the GT3, since the high altitude effectively lowers the compression and need for octane). And for Turbo cars, there's the option of E85...

stout

91-octane gas significantly reduced my enjoyment of my GT4, causing a torque trough from 3000~ to 5500 rpm that I didn't experience in Euro GT4s or my car after the computer was reset. A week later, it was back. Ditto for a friend with a GT4 locally. ECU reset and no more flat spot...for about a week until the computer learned it didn't like CA 91.

One wonders why fuel sellers even bother with the 89 button in the middle? Does anyone actually buy the mid-grade stuff? Would be so much better if gas stations offered 87 regular, 91 premium, and 93 performance. They might even make more money off of 93 or 95 than they do from the mid-grade stuff...

Christmas50

You'll be suprised. Is not just once I've seen people filling up 87 or 89 in brand new Mercedes Benz

Ryan_G

The 89 is just a mixture of 87 and 91. In states with 93 any grade between 87 and 93 is simply a mixture of 87 and 93. That way they only need 2 tanks in the ground. They offer it because whenever someone buys it they make a better margin.

d00d

Higher octane is available in the West, mix with 91 to make it more affordable;
https://find93.com/

Christmas50

We have 100 near me but is $10 bucks a gallon

NoGaBiker

jmartpr

I did several COBB datalogs with John from BGB trying to diagnose a timing issue and the limits of tuning on really hot weather...it all went back to the quality of the gas.
The GT4 is right on the edge of detonation and any correction will pull the ignition back several degrees...so you are belter off starting with less advanced timing than allowing the ECU to adjust if your gas is not up to specs.
Try to find the best gas you can.....93 is the best but is has to be pure 93 not the ethanol mixtures as we found that 93 octane but with 10% ethanol (which really is a 91 with some ethanol) is a no-go on the GT4.....on the other hand our F80 M3 ZCP loves that stuff.
I found a good 93 gas station and always fill up there...and for the track I fill with Sunoco GT260 which is 100-octane unleaded, just for safely but it gets very expensive.
Porsche also recently launched the Kerapur gasoline additive.....according to the service department at my dealer they had to provide these to different markets and they rank 1,2 3 the quality of the gas on that market....ours rank 3 so you can imagine and they highly recommend using Kerapur on every fill-up.

ExMB

That sounds more like something the dealer is pushing than Porsche. It doesn't appear on this list.

jmartpr

Maybe....but since it's branded as a PAG product I decided to purchase some in case I can't get to good gas. Now... I can't prove it actually works but its better to have it than not if the gas is not going to be 93 octane.
As for not being on that list it could be produce and marketed by other company...and Porsche just re-labels it....don't know.
Let me see if I can find the literature for it.....

jmartpr

Ohhh, my bad.... is Keropur and manufactured by BASF

digitalrurouni

I can totally feel the difference on my bikes with ethanol free 93 octane vs 93 with ethanol. Bike feels like it's just got more torque across all the gears so it accelerates harder for the same amount of twist I give it. It's a great feeling so I usually fill up at that gas station that's up in the mountains on my ride back. I should start doing that with my Spyder next time I am up there. I should probably take some cans and fill them up and bring them back with me!

Gatte

jmartpr

Agreed....anyway, the 4.0L NA 6-cyl will fix any issues with bad gas!!!!!!!