Quick question for all you techies out there. I new the the RX-8 world, lovin the car so far. My question is about the gas Octane, is it better to use premium (91), or does it matter if you use 87. Whats the difference in performance?

 

You should actually put cream instead of octane, it really performs MUCH better!

Really!.. i am not kidding.


NO REALLY! I am serious!

 

 

How rude!

Fine...

 

Wait... what?

 

You should use the cheapest octane that your car runs good on. This is one area where different cars respond a bit differently. Some people report having no issues whatsoever with 87 octane while others say their car runs rough with it and can only use 91 or so. Nonturbo rotaries have always loved low octane but the RX-8 ecu changes that somewhat. Try them all and then use the one that works good for you. This isn't oil. There's no benefit to paying more for higher grade if you don't have to. If your car runs good on 87, use it. The owners manual recommends premium but by no means does the word "recommend" imply "must". It is a guideline and we all know how many guidelines out there we don't adhere to. It's nothing more than a safe recommendation on Mazda's part to cover all the markets as the quality of fuel across the country varies between octanes, markets, and even the time of year. While 87 may be fine in Houston, 87 in California may have a totally different formulation and not work as well. You get the idea. By recommending a higher octane level, they pretty much eliminate all variances and cover everyone. Use the cheapest stuff that works fine to avoid wasting your money. Higher octane does not mean higher power.

 

I use 91... and who doesn't want to be like me?

 

I use 93, me > you!

 

What I found to be more important than octane was the brand of gas I used; after testing all the brands available in my area (Southern California) I've found Shell gas to give me the best performance. Second choice would be Chevron. Shell 87 ran better in my car than Arco 91 just as an example.

 

i use 93, some sunoco's will have 94 so whatever is higher. i once saw a 98 octane gas somewhere in jersey but i didnt dare put it on.

 

They dont sell 93 here.

 

Thanks for the reply's

 

Yeah, that Shell gas is the BEST!

It's all I use.

S

 

Shell 93 V-powa ftw.

 

I've used 93 since I drove her off the lot.

 

http://www.cars.com/carsapp/national...odaysgas1.tmpl

Before i bought my 8 I had a 2002 Jetta. Before I sold the car the check engine light came so I had it checked out before I sold it. I inquired about the repairs and the service manager asked me if I used low octane fuel...I said yes, because my car didn't require a high octane. He informed me that low octane fuel will cause your catalytic converter to go bad sooner than if you used high octane fuel.

 

I think that's a load of crap personally.

My Honda actually hates Shell. It runs terrible on it. Really strange.

 

Maybe it's a state by state thing.
Shell/chevron seems to be the best in california for me. Arco sucks, but wel all know that :]

 

I've always thought it was a load of crap as well. I've always filled up at whatever gas station was closest. Howevere I noticed my car felt a touch stronger and smoother and just wrote it off, then had the same thing happen a few weeks later, I realized the only difference was I had filled up at Shell. I don't go far out of my way to get Shell, but if I have a choice and I know there's a Shell station close by I'll always pick Shell.

 

Since you live in Wisconsin do you have a Clark station near you?? My mom's Protege always did so much better mileage and performance wise when she bought it there as opposed to the other stations around.

 

I do agree with you for the most part and understand why the lower oct. works best in the old rotarys but with the 8's higher compression I do think that the higher oct could allow more spark advance and there for more power. Unfortunately there is little proven evidence of this since most these posts are opinions whether they be right or wrong.

 

The Clark stations around Chicago have changed over to Marathon. My car dosn't like Marathon gas.

With the RX7's we could adjust the timing with the distributer and get the most advance with 87/89 octane. With the RX8 it is all computer controlled. You would think that would give you the optimal setting. But once the computer senses pre-detenation it may retard the timing more than necessary to preserve the engine.

 

I haven't been to Wisconsin in about six years so I have no idea if they still have them around or not unless I ask a relative.

 

i use 89 octane... cheaper then 93 and don't have to worry about pinging with my cz installed on 87

the computer doesn't advance the timing any more on 93 octane then 89 octane (never tried 87 octane)

 

The RX-8 compression ratio may be physically higher on paper (by only a fraction) at 10.0:1 vs 9.7:1, but in truth the larger seal clearances cause much more leakage in the Renesis and the higher compression actually doesn't quite even that out. Also consider that with no overlap, there is less exhaust heat/dilution carried back into the intake side to affect combustion. Due to this you should actually be able to get away with a lower octane before ping sets in. The only thing affecting the car is the ecu tuning but it's been a pain in the butt for everything else as well. If it were tuned better, the car could quite easily run all day long on low octane fuel and some actually do.