87, 89, 91, what's the best fuel?
01-18-2006 | 05:48 PM
#1
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From: Escondido
87, 89, 91, what's the best fuel?
I know Mazda says use 91. I've searched the forum and seen 10 people with 10 different results on using different grade octane. Has anyone actually dyno'ed there car on different grades to see if there is an actual difference? Right now i run 91 and i've seen most of the people on here run 87, i was gonna start stepping down the grade to 89, maybe even 87, i just wanna make sure i dont have any detonation problems. Please let me know. A dyno graph would be awesome.
Whitey
Whitey
01-18-2006 | 06:20 PM
#3
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the diff between 87 and 91 is about 10 cents a gallon which translates to about $1.50 max more per tank. Its a frickin $1.50. I'de rather have the extra power and also know that no matter what the ECU may do, I won't have worry at all about pinging. Again, its a buck fifty.
01-18-2006 | 06:29 PM
#4
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From: Escondido
I never made a complaint about saving money on gas. I just wanted to know if anyone has any technical proof that one gas is more efficient with the renesis than another. I know Scott from Mazsport was saying that when he builds a rotary beast he builds it to run on 87, so i was trying to find out if the renesis in its natural form likes 87.
Whitey
Whitey
01-18-2006 | 07:22 PM
#5
you might read around this thread.
start here and read about 5 pages after. lots of info.
https://www.rx8club.com/showthread.p...ht=interceptor
pay big attention to this post!!!
https://www.rx8club.com/showpost.php...&postcount=480
hope this helps. btw i have pretty much run 87 in my car since new. good 87, but 87. a couple of time i have run 93 just to clean, and one can of b@g 44k for cleaning.
40k miles, mpg ave of all tanks is ~21 mpg.
hope this helps
beers
start here and read about 5 pages after. lots of info.
https://www.rx8club.com/showthread.p...ht=interceptor
pay big attention to this post!!!
https://www.rx8club.com/showpost.php...&postcount=480
hope this helps. btw i have pretty much run 87 in my car since new. good 87, but 87. a couple of time i have run 93 just to clean, and one can of b@g 44k for cleaning.
40k miles, mpg ave of all tanks is ~21 mpg.
hope this helps
beers
01-19-2006 | 12:01 AM
#8
Thread Starter
Registered User
Joined: Dec 2005
Posts: 48
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From: Escondido
Originally Posted by swoope
you might read around this thread.
start here and read about 5 pages after. lots of info.
https://www.rx8club.com/showthread.p...ht=interceptor
pay big attention to this post!!!
https://www.rx8club.com/showpost.php...&postcount=480
hope this helps. btw i have pretty much run 87 in my car since new. good 87, but 87. a couple of time i have run 93 just to clean, and one can of b@g 44k for cleaning.
40k miles, mpg ave of all tanks is ~21 mpg.
hope this helps
beers
start here and read about 5 pages after. lots of info.
https://www.rx8club.com/showthread.p...ht=interceptor
pay big attention to this post!!!
https://www.rx8club.com/showpost.php...&postcount=480
hope this helps. btw i have pretty much run 87 in my car since new. good 87, but 87. a couple of time i have run 93 just to clean, and one can of b@g 44k for cleaning.
40k miles, mpg ave of all tanks is ~21 mpg.
hope this helps
beers
01-19-2006 | 12:24 AM
#11
Lubricious
Joined: Oct 2003
Posts: 3,425
Likes: 4
From: SF Bay Area, California
Originally Posted by chikmag382
I know Mazda says use 91.
I've searched the forum and seen 10 people with 10 different results on using different grade octane. Has anyone actually dyno'ed there car on different grades to see if there is an actual difference? Right now i run 91 and i've seen most of the people on here run 87, i was gonna start stepping down the grade to 89, maybe even 87, i just wanna make sure i dont have any detonation problems. Please let me know. A dyno graph would be awesome.
Whitey
Whitey
I've used 87 for all but one or two tanks right after I got the car two years ago. I've never had knocking that I've noticed and power seems fine. I've driven in temps into the triple digits. Most of my driving is near sea-level elevation.
Last edited by Nubo; 01-19-2006 at 12:27 AM.
01-19-2006 | 12:29 AM
#12
Originally Posted by djseto
the diff between 87 and 91 is about 10 cents a gallon which translates to about $1.50 max more per tank. Its a frickin $1.50. I'de rather have the extra power and also know that no matter what the ECU may do, I won't have worry at all about pinging. Again, its a buck fifty.
beers
01-19-2006 | 01:08 AM
#18
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Joined: Nov 2003
Posts: 3,281
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From: Glendale, CA
Has anybody done a dyno on the Renesis with different grades of gasoline ? No.
Has it been done before. Yes. I posted an article from Car & Driver on several of the threads discussing this subject. On cars set to run 87, going to higher octane made little difference. On cars set to run 91 octane & filled with 87 there was a big difference. Cars set to run on 91 will automatically lower timing on the engine when it senses knock/detonation. That knocking would almost be imperceptible to us before the car did this. These are carbuerated cars these days where we have to do it manually. The ECU constantly adjusts this. In the test the Saab Turbo & M3 lost about 10% of their power with the switch in gasoline. Depends on how sophiticated you think our engine is. Is it closer to an M3, or a Mustang GT engine. High compression has a play into as well.
Has it been done before. Yes. I posted an article from Car & Driver on several of the threads discussing this subject. On cars set to run 87, going to higher octane made little difference. On cars set to run 91 octane & filled with 87 there was a big difference. Cars set to run on 91 will automatically lower timing on the engine when it senses knock/detonation. That knocking would almost be imperceptible to us before the car did this. These are carbuerated cars these days where we have to do it manually. The ECU constantly adjusts this. In the test the Saab Turbo & M3 lost about 10% of their power with the switch in gasoline. Depends on how sophiticated you think our engine is. Is it closer to an M3, or a Mustang GT engine. High compression has a play into as well.
01-19-2006 | 01:39 PM
#19
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Posts: n/a
Originally Posted by chikmag382
I never made a complaint about saving money on gas. I just wanted to know if anyone has any technical proof that one gas is more efficient with the renesis than another. I know Scott from Mazsport was saying that when he builds a rotary beast he builds it to run on 87, so i was trying to find out if the renesis in its natural form likes 87.
Whitey
Whitey
The owners manual says that for best performance you should use 91 or 93. This is based on lots of testing and engineering. Maybe I am biased since I have an engineering background, but Mazda doesn't have monkeys doing their work, so I believe it when it says to use the higher octane for best performance. Recommending it vs. requiring it are different. Cars that require a higher octane will have problems with 87 because of the rate at which the fuel burns, but cars that only require 87 won't suffer any real issues if you use 91 or 93. I just go with what the manufacturer says on this issue. As for gas mileage, thats a whole other debate. I don't know much about what Mazsport does, but unless his engine is completely stock, I don't know if I would use that as a baseline for your decision. Your engine, as delivered straight from Japan, is probably going to perform best on 91/93.
01-19-2006 | 01:48 PM
#20
The shadows of an 8
Joined: May 2005
Posts: 66
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From: Louisville. KY
I was told by the dealer and he gave some print out from Mazda that says prefered 93 octane but 89 would be ok. I t also said not to use 87 because it could cause vapor lock in hot weather. 
I also read some where it also could cause predetination.
I also read some where it also could cause predetination.
01-19-2006 | 06:26 PM
#24
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From: Escondido
Well, I guess until I get the Interceptor-X I'll just stick with 91. The slight extra cost is of no significance to me, I've just come across a bunch of threads where the most power was made with 87, but like fanman said, until your car is tuned to run on a lower grade, 91 is the better way to go.
01-19-2006 | 06:34 PM
#25
note,
i have been running 87 since i got the car. i only had the car with the xeptor on for a drive for about 45min. i do think i would not run 87 in cali or anywhere that has a winter blend. but i would try it for a tank or 2.
the issue i mentioned with my bike. zuki recommends 91 bike would have idle issues and do something we call fart stall.
run 87 in it and it runs perfect.
beers
i have been running 87 since i got the car. i only had the car with the xeptor on for a drive for about 45min. i do think i would not run 87 in cali or anywhere that has a winter blend. but i would try it for a tank or 2.
the issue i mentioned with my bike. zuki recommends 91 bike would have idle issues and do something we call fart stall.
run 87 in it and it runs perfect.
beers