Well, I'm experiementing with my first tank of 87 Octane fuel in my -8. I know a lot of you use this, and successfully, others swear by their VPower or Ultimate or whatnot ...

I've been a dedicated 93 Octane user for 9 years now - two Acuras, and now 3 months with my -8 but yesterday when I filled my -8 up, the neighborhood shell was out of VPower, and rather than drive to another station (all of a block away ... yes, lazy), I just punched the "87" button, crossed my fingers and went for it.

So, what will I experience? Will I go blind? Grow hair on my palms? Will the sun stop rising in the east?

So far, no "feelable/hearable" difference in performance - have done a few WOT acceleration runs and all seems fine. I'll be interested in seeing the gas mileage numbers -

Who else uses 87 octane gas?

 

Since it's cooler out now, you'll probably be fine. If it was in the middle of summer I'd be a lot more concerned with pinging- several people on this board had issues with 87 octane in the heat. I've just dropped down from 93 to 89 since heat is no longer a concern around here... but as much heat as the rotary is capable of developing on hard runs I'm too much of wimp to go any lower.

 

Well, if my engine falls out on one of my "drives" you'll probably run over it seeing as we frequent the same fun roads ...

Hadn't thought about the heat as an issue, but now that you raise it - makes sense. I would think that the more volatile regular gas would assist in cold starting ...

 

I'm using 87 for a couple thousand miles now - didn't have any problems so far and the car performs just fine. No noticeable difference but then I'm not driving like a maniac either

 

I get MUCH better mileage outta 87 oct. (much meaning about 2-4mpg more.) but your mileage may vary.

 

I've been using Shell 87 octane for a year now and my car runs beautifully. I especially appreciate that since the price of regular gas here has been jumping 10 cents a gallon every week; yesterday it was $2.44 a gallon....took $31 just to fill up.

 

Damn you guys in Cali get raped on gas... I thought it was bad in Chitown. I do get slightly better mileage with 89, so it makes sense that 87 might be an increased improvement.

 

see my sig. I think it's been about 10,000 miles for me. I got premium same price as regular on a tank recently and that tank was lower by about 2MPG. It may have something to do with the PCM. I didn't try to 'reset' it. Premium would have to give me enough of an increase in MPG to make up the cost. It doesn't. IF I ever get to take it to the track where a 1/10 second here or there might matter that I can pick up on premium I might use it for that purpose.

 

Sorry, I'm confused. Premium gets worse mileage than regular, not better.

 

Why does 91 Oct make the mileage worst than regular? If the engine is designed for 91 why didn't Mazda say that if we put in lower Octs than the mileage would improve? Are we talking about cold winter driving only?

 

Probably a dumb question:

Is it bad to alternate between 87 oct and 91+ oct? I had always heard of small cars using 87 most of the time then using 91 once in a while to "clean out the engine". Then again I could be talking to idiots

 

Higher octane fuels don't help fuel economy at all- they simply resist detonation better. This is why cars with higher compression or higher heat (performance cars, turbo's, etc) should run premium as a safety factor, to prevent potentially damaging pinging... and better performance from being able to withstand the higher heat and compression.

Many of the gas companies also throw in some nifty cleaning additives to help market their premium fuels... like Shell's V-Power.

 

There is a thread about this already. There was an article that I had posted from Car & Driver when they ran cars that normally ran 87 they gained a few hp. When they put 87 in cars that were meant for cars that recommended 91 octane the PCM dialed down power 8%-10%. RX-8 have a recommendation for 91 (section 4-13). The PCM will compensate for the lower octane fuel and retard the timing down a bit, but people who have gotten some 87 octane reported detonation. I think that is about as far down as the PCM will go.

 

If they're using 91 on an engine designed for 87, the only thing they're cleaning out is their wallet.

 

I use 87 a lot, but I have realized that I mostly get better mileage with 91. Nowadays, I only use 87 if I don't feel like spending so much on gas.