Mixing Octane
 

In AZ the best octane we get is 91 octane. There are a few places that carry 100 octane. A friend of mine suggested that I pump a gallon of 100 then fill the rest with 91 and I should come out close to 93. Any one have any thoughts on this?

Is it okay to mix octanes like that?

I think its okay to mix the octane, but I don't know how well they mix. How do you "shake" up the gas tank?

And I think according to the formulas, you'll need more than 1 gallon of 100 octane for 14 gallons of 91 to get to 93. :)

I'm no rocket scientist or anything, but if I wanted 93-94oct I would put in around 2parts 100oct for every 3 parts 91:) or 2/3rd's 91 and 1/3rd 100, roughly speaking of course. That should be in the ballpark.

I can buy 104 octane here in MI but have been nervous that i may screw somthing up does anyone have any info on this? I run it in my Hayabusa without problem, just not sure about the Porsche

I've talked to people about using higher than recommended octane levels, and they don't suggest it. Your car is tuned to run at a particular octane. Gasoline with too high octane will cause deposits on your intakes and cylinders.

Just my two cents.

I'll probably just keep running 91. Car seems to be fine so far and it's 3.5 years old.

Aesir,

When I lived in AZ, I mixed 100 octane exactly ONCE (Texaco on Bell Rd). I added 2 gallons($10) and then topped up the tank with 91. I couldn't tell the difference, so I decided to skip the hassle.

If I were going to do 1/4 mile runs, I MIGHT try 100 octane, but I don't do that kind of thing to my car.

P.S> linnig in NY, now I just buy 93/94 octane :) at the pump :)

you need 3 gallons (100) with 13 gallons (91)
 

= 18.75% (100) +81.25% (91)

And if you want an "official" answer on the idea of mixing octanes, look here. Sunoco apparently confirms it to be a straight "by volume" mix. I thought I'd heard otherwise before, but here it is from (one of) the horse's mouth.

Nice, thanks everyone!

Here in Maryland I only find 93, but I have seen 101, however it was racing fuel that contained lead, just be careful not to get any of that in the engine.