91 or 93 octane??
 

does the RX8 perform as well on 91 as it does on 93+?

does heat affect the car much?

Yes.

Maybe

Yes, 91 octane is fine. Yes, high temps affect the performance in all cars.

I use 93 octane. Cause it's more than 91, which is always better. More is better.

on my current car switching from 91 to 93 nets about 20 WHEEL hp. gas is a killer on my S60R. little turbo engine with knock sensitivity...

also, heat is ak iller. the car loses probably 40hp in 80+ degrees.

Perhaps I missed the sarcasm there. :)

We generally have 92 here and some stations have 91. I haven't seen a station in my area with 93 or higher. I haven't noticed a significant decrease in my car due to heat, but I do notice one when its near freezing and below. Then it really drinks up the gas and has a feeling of less power. It just feels like it is trying much harder than it does when it is warmer.

Wow, sucks to live in Miami then. 80F+ is our average..

Na, I haven't seen below 93 here. It's always 93+ around.. And well, I drive in warm warm weather.. Everyday. Except on some lucky ones that get as low as 50-60 for one night, which I celebrate, then the next day-- back to the high 80s..

i don't have much of a choice since the highest pump gas we have is 91..

You're using Oxygenated Winter Blend of gas (So does everybody in the US). It sucks for MPG but its better for emission. Everything should be back to normal As soon as Around March.

Heat kills everything.

I'm aware of that, but the colder it gets outside, the worse it does also. This current tank of gas I've gone through 1/4 of a tank so far, and it is 20 miles behind it's usual spot for my "winter" mileage range. If it continues at this pace I may hit 18 if I'm lucky. Otherwise I've been getting mid 19s to mid 20s. It's been around freezing and below this whole tank, with our little storm and all. Last night it was 16 degrees when I got home. When I left work it was 21. It took between 5-6 miles before my needle hit it's "warmed up" spot on the temperature gauge, where it's usually fully warm by the time I get to the end of my road (1.7 miles) even in our cold temperatures. On take off the car feels a little sluggish to get going, but when it warms up to 40 and above, it feels just fine. I don't think Bella likes this cold. I already know she doesn't like the gas.

When it gets below 70 hear in the winter I can use 89 octane. In the summer when it's 125+ I can only use 91 octane and still I get pinging if the car idles for more then 3-5 minutes and you push on the pedal to accelarate. I wish we had 93 octane.
I haven't noticed a difference in 89 and 91 in the performance end of it. Just the ping end of it.

If you have FI in your car, it might make a bit of difference.
but if you want better fuel performance with FI, get 100+ octane.

With NA engines, it shouldn't do much.

I've read that some stations in the Bay Area have 93. Unfortunately I don't live near any. :mad:

Why is 93 so hard to find in Cali?

I don't worry too much about mileage when driving my 7 or 8 but I do notice a slight improvement in performance-turbos like cooler/denser air and the 8 simply stays a cooler. I'm stuck with 91 gas though.

I use 89 and it works fine. I also don't live in the Utah desert though. There are some other more technical threads around here about octane. Search and you'll find them.

Your gas mileage goes down in the colder weather because the cold air is more dense so to maintain the same fuel air ratio the computer injects more fuel. It also means it makes more power. That's the same premise as using an intercooler on a Forced Induction car.

Thanks for the good explanation! :) I always knew that mileage got worse the colder it got, but I didn't know why. My car does it's best over 60 degrees and then starts to go down again in the high 90s, which we don't get much of.

I don't think theres much difference in 91 and 93 octane.. Never used lower than 93 cause I can't find any lower here.. Maybe it's the heat? Anyways, yea.. I'm not bragging.. :)

I've run 87 since I bought the car. 93 has shown no or maybe less performance/mpg for me. There are a lot of threads on this issue but if you don't experience pinging with 87 then go with it.