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What fuel is best for an RX8?

Old 12-19-2004, 11:36 PM
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What fuel is best for an RX8?

I was curious what octane I should be sticking in a rotary, obviously for turbocharged the highest possible octane but with the Renesis I wasn't sure.

BTW I do not own one but I was just curious.
Yet...
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Old 12-19-2004, 11:43 PM
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The manual says 91 octane
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Old 12-20-2004, 01:38 AM
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Here downunder, most owners use 98 octane in the 8.
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Old 12-20-2004, 03:29 AM
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Hate to say do a search, but this topic has been discussed in much detail. If you are looking for max performance go with 93/91 octane at all times. It can use 87 or 89 but the ECU will retard timing and decrease your hp, especially under heavy throttle. I had included an article in the previous threads where they tested several cars, and the ones that recommended/required 91 lost 6% to 10% of their performance when a lower grade of gasoline was used.
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Old 12-20-2004, 03:56 AM
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Man, you guys are up late. Makes you do crazy things like bring up over-discussed topics.
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Old 12-20-2004, 04:09 AM
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Processed petrol from your local gasoline station is the best fuel for your RX-8.
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Old 12-20-2004, 05:22 AM
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Originally Posted by Equis
Processed petrol from your local gasoline station is the best fuel for your RX-8.
ROFL! :D
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Old 12-20-2004, 06:04 AM
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Originally Posted by Virgil
I was curious what octane I should be sticking in a rotary, obviously for turbocharged the highest possible octane but with the Renesis I wasn't sure.

BTW I do not own one but I was just curious.
Yet...
93 octane
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Old 12-20-2004, 07:30 AM
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I just added up the number of tankfuls of 87 octane in my gas mileage spreadsheet and I counted 65. (I counted 16 tanks of 93). The difference in performance was negligible - if anything it was better with 87 than with 93. There are technical arguments as to why this might be true due to the shape of the rotary's combustion chamber that I don't completely understand. All I know is that 87 works best for me.
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Old 12-20-2004, 08:30 AM
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I experimented with 87 once. I also learned my lesson by experiencing engine knock at high rpm/WOT! Bad sound, that. It also didn't feel as snappy on the 87, probably due to the retarded spark. I also have an '83 RX-7 that is the opposite - dyno proven to make more power (4hp) on 87 vs 93. No knock ever on the 12A, even when spark was accidentally 10 degrees advanced.
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Old 12-20-2004, 08:40 AM
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I use 89/91 (whatever the mid grade is) at the more expensive stations, but if I have to go to a cheaper one I get the high grade, haven't noticed a difference between them
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Old 12-20-2004, 09:58 AM
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Originally Posted by pmrobert
I experimented with 87 once. I also learned my lesson by experiencing engine knock at high rpm/WOT! Bad sound, that. It also didn't feel as snappy on the 87, probably due to the retarded spark.
I experienced the exact same problems, and they were all due to using low-grade fuel. I took it to the dealer, they told me to switch back to 91+ octane fuel, and the problems, for the most part, have since been resolved. I'll never go back to 87 again and would dissuade anyone from putting it in their 8's.
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Old 12-20-2004, 05:18 PM
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Some in outback Oz use koala oil and refined kangaroo poo, some of us even use 98 Premium unleaded and there is a marked difference in performance from the normal 95 octane fuel..
My Mazda3 Sp23 also runs 98 premium fuel and there is a significant increase in power in this OZ spec vehicle.9100RPM
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Old 12-20-2004, 07:24 PM
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95 is normal in Australia?? Geeze, I bet that's really expensive. 93 is the highest we hit here in the US (I think).

And refined kangapoo? I bet the exhaust wreaks!
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Old 12-20-2004, 07:52 PM
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Talking

93 Always! Be good to your car!
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Old 12-20-2004, 08:18 PM
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Originally Posted by markd
.......I'll never go back to 87 again and would dissuade anyone from putting it in their 8's.
LOL! 87 octane from 2nd tank on, 15k miles and no problems related to fuel or engine.

If I lived in the red line zone, I don't think I'd use 87 octane though (from what I've read on the forum) - but for my driving style it works just fine. I'll take the $$$ in fuel saving over a few HP, thanks.

Anyone here using 87 octane and living in the red line zone with no issues?

Last edited by rx8cited; 12-20-2004 at 08:53 PM.
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Old 12-20-2004, 08:50 PM
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Originally Posted by Xrated
93 Always! Be good to your car!

I strongly agree.
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Old 12-20-2004, 08:58 PM
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If the manual says that low octane will work find then guess what. Low octane will work fine. No suprises here.

As for the guy who says he had engine knocking and went to 93 and "for the most part the problem went away". You've got big problems in there. Good luck..
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Old 12-20-2004, 09:33 PM
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93 for my baby!! Specifically...Shell V-Power. :D

- Irish
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Old 12-20-2004, 09:59 PM
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I've used 87 and did not notice much difference in power, but my mileage dropped significantly... I only managed 147miles to 14.8 gallons. My fuel light had been on for a little while, and I could not believe when I filled up that I was that close to empty and had only 147 on the trip meter. Thats right....9.8mpg.
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Old 12-21-2004, 02:54 AM
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Originally Posted by markd
95 is normal in Australia?? Geeze, I bet that's really expensive.
95/98 octane is about $1.10 per litre here in Sydney Australia.
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Old 12-21-2004, 08:17 AM
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Originally Posted by 8_is_enuf
If the manual says that low octane will work find then guess what. Low octane will work fine. No suprises here.

As for the guy who says he had engine knocking and went to 93 and "for the most part the problem went away". You've got big problems in there. Good luck..
"You've got big problems in there"???? What the hell is that suppose to mean? I surely hope you did not mean that derogatorily. After having read feedback from numerous respected individuals on this forum, the service manager of my dealership, and other Mazda mechanics since, as well as my own personal observations of my engine's performance using various octane fuels, I don't believe my comments on 87 vs. 93 are baseless. Considering I'm not alone in my position, you're otherwise also calling several other 8 owners crazy.
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Old 12-21-2004, 08:49 AM
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Mark D

Feel free to read your post again, then mine. Not sure how you can get offended over this, but knock yourself out. (Actually kinda funny to me -- like Captain Furious in the movie Mystery Men.)

You said you engine was knocking at High RPM's with low octane fuel. You went to the higher octane and it "for the most part, has been resolved." If your engine is knocking at any RPM "Bad Sound" then you have a problem.
And if using better gas helped but didn't fix the problem, it soulds like a band-aid on a problem that will get worse.
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Old 12-21-2004, 09:10 AM
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Originally Posted by rx8cited
Anyone here using 87 octane and living in the red line zone with no issues?

I have been using 87 octane pretty much since I got the car. I live in the red-line zone and have not had any issues, although if I put 93 octane in...it just gets there smoother and what seems like faster (have not clocked this). I get about the same number of miles on the tank (220-260) no matter what I use with the exception of last week and the freezing weather which dropped me down to 160 miles on the tank...this I still don't completely understand.
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Old 12-21-2004, 09:19 AM
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Originally Posted by nojooc
95/98 octane is about $1.10 per litre here in Sydney Australia.
Damn...that works out to 4.26 a gallon
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