redyps

Joe -

5 gals are $41. Lasts 2 sessions. I bought 5 gals twice and then one 3 gals. Went to the Chevron in Willows on the way home.

stevecolletti

The manual on the Cayman recommends 93-octane - same as the RS. The difference is that the Cayman manual shows 90-octane as the minimum, the RS shows 91-octane. I can't find fuel higher than 91 (other than the 100-octane race gas) in Kali - actually anywhere west of San Antonio. Based on this, I would expect the computer to recognize and use the higher octane (at least up to the 93 number).

With the RS, I use a ratio of 1 gallon of 100-octane to just less than 3 gallons of 91-octane. With that car, the difference is quite noticeable, even on the street.

Now that my throttle issue is resolved (separate post), I'll try the same ratio with the Cayman.

orthojoe

Steve, do you think there is any advantage to running octane any greater than 93?

stevecolletti

On that, I can only speak to the RS, at this point, as the tank of 100-octane I put in the Cayman as a throttle diagnosis tool made no real difference. I will be trying it in the Cayman again on the next tank.

As for the RS, I picked it up in Houston in July (2009). It was 100+ degrees all the way into LA. Once I lost 93-octane, somewhere in West Texas (it existed in San Antonio, but was extinct at my fuel stop prior to El Paso), the car ran completely differently, noticeably down on power/torque, and less responsive. I also got a hint of ping at one point.

That car now has SharkWerks DME in it (tuned for 91-octane, not 93, which makes a couple more HP). I did it to remove the eGas delay as much as possible.

When I spoke with Alex, I'm pretty sure he said that the DME (even stock) will take advantage of up to 95-octane).

Running pure 100-octane seems to make no difference on that car (before or after DME). I think (honest) 93-octane, if it's available, would be fine for daily driving. If I take that car to the track on a hot day, I'll run a 50-50 mix of 100:91 just to be sure.

My big worry on these car, where the manual states 93-octane, is the stations that aren't really providing 91-octane. I got a terrible tank of 91-octane gas from a Chevron station in Morro Bay on the way up to Monterey, last year.

I'll let you know what I notice on the Cayman, but I'll be surprised if I notice anything while we're in the 60-70 degree range.