blknfury

what happens if you dont use premium gas in your 93-95 fd and use regular? my friend has a 96 supercharged mustang cobra and he uses regular. he has never had any problems with his engine

sonix7

you should really try a search first!! Here you go. a few threads on it.
https://www.rx7club.com/3rd-generation-specific-1993-2002-16/what-do-you-guys-think-fuel-463830/
https://www.rx7club.com/showthread.p...on+octane+fuel

nopistons94

you don't have to bother searching. Do it and boost and your motor won't run long.

2FAST7S

Not necessarily...run low boost levels and if you have a stand alone ecu tune it to run safe on lower octane gas. You will not make too much power and if you do youre chances of detonating are increased thats all

sonix7

I love it! you might pop the engine, but that's all. I am freaking out about using my shitty pump crack 91 oct., so maybe that sheds some light. I am stock with DP, intake. I am hoping for the extra reassurance of keeping out of danger.

rynberg

If you are worried about premium gas, sell the ******* car. How's that for a simple answer?

sonix7: I told you this in your previous thread but you have zero to worry about running around on 91 octane with the stock ecu.

legal-z

I Agree 100%. even if premium is $.40 more a gallon, you're talking about maybe an extra 12 bucks a week and that's if you're driving almost 400 miles a week with your car. if you can't afford an extra $12 a week, you can't afford an fd. you'd have to run on 87 octane without blowing up for almost 5 years to save enough on gas to equal the cost of the motor you're going to have to replace when it pings. and that's figuring only $3000 for a rebuild and associated parts and labor (which is a lowball estimate) divided by the $12/week you're saving.

where i am, premium is only about $.15 more a gallon, which makes the above numbers look even more rediculous when trying to justify using 87 octane.

sonix7

Thats fine and I respect your advice, I am just trying to learn as much as I can about this. I know you are not madd at me for that? I am not tripping out, I just don't like what I heard about low octane gas, like regular unleaded which is like 87 octane out here.Then after reading about gas pumps advertising the RON and not the actual octane got me a little worried. Is 91 octane really 91 octane or in the high 80's. See what I am saying? I just did my hose job and threw on an intake, I am flowing real nice on boost and the other day I saw it spike up. I just want to make sure the dense *** air up here and my mods don't cause me my original 45,000 mile engine. Feel me? I am educating myself through you all, please be patient with me. Sorry if I have asked questions more than once, I want everyones opinions. thanx guys.

rynberg

NO! The US does NOT advertise RON only, like other countries do. The displayed octane is the average between the RON (research octane) and the MON (motor octane). Any of the good national brands (Shell, Chevron, 76) will err on the side of caution with these octanes. Some tests of random stations have shown the actual octane being about 1 point higher than advertised.

If you are buying 91 octane, that's what you are getting! (barring a mistake in filling the pumps..)

The air is LESS dense if you live at higher altitude = car running richer = car running "safer". You have nothing to worry about! If you are that concerned about it, then either stop modding or move on to a different vehicle.

No anger here, just getting sick of misinformation being passed along.

sonix7

thank you for correcting me on my mistake. I am just trying to learn, not spread mis-information, all I have been inquiring about is the truth. thank you for helping me. I understand your frustration. Its cool.

t-von

iTrader: (8)

What a load of crap. Do you actually think Mazda would really expect it's customers to solely run the recommended 91 octane in their Rx7? Every manufacturer programs there ecu's to leave a margin of safety for lower grade fuels. Mazda would be stupid to not program the ecu this way. Otherwise every Rx7 they build would have stock engines that would need rebuilding because someone put in 87 octane. Mazda isn't stupid enough to put themselves in those kinds of warranty related issues. This is one of the main reasons the stock ecu runs so rich under boost. Thats how they compensate for lower grades of fuel if they are actually used. You can actually drive the car with 87 octane and boost it. Just make sure your car is stock with stock boost levels with no modifications. I have 98k original miles and currently have 89 in my car right now with no ill effects. I would go down to 87 (because of fuel prices)but I have a down pipe and modified stock air intake with manual boost controller. I don't think the ecu will compensate for this with 87 in the tank since I get a small spike to 11psi during transition. If I was 100% stock I wouldn't worry about it.

BLKTOPTRVL

Hmmm, around here, regular is 2.88 and premium is 3.08. For a 7% difference. I don't see that it is worth taking the chance. However, if you read the manual, it says you can run the car on less than premium gas. It should compensate for the lack of octane.

But my question is, do YOU really want to take the chance of destroying an engine for the extra cost of premium over a year? (~$90 - $100)

Not worth it if you ask me. What it comes down to really is, you can't afford the car. Sell it before you destroy it.

t-von

iTrader: (8)

The price difference doesn't change the fact that it is perfectly safe in a completely stock car. Too many people on this forum are just plain paranoid.

Sgtblue

iTrader: (16)

My car is also still close to stock. And I'm aware that the stock ECU is set a bit rich as a safetu margin. But this is not to say that I want to test it. IMHO, it's not worth it. I spend a couple of extra bucks to get decent oil, a good filter and I'm generaly careful about maintenance. Why would I buy 87 or even 89 in order to save what....a dollar on the average fill-up? As my engine gets older I tend to want more of a safety margin, not less.

sonix7

my point exactly, that is why I have been inquiring about higher than 91 oct. safety measures. Not that I am scared, because I treat my car like a baby, I want it to be happy and healthy.

nopistons94

dude honestly, your ******* retarted. You go run your 89 or 87 and enjoy. :thumbsup:

mesallem

It's ok to run 87 octane. Your engine is tuned to 91, meaning your compression and detonation of your air fuel mixture are made for 91. If you accidently put 87 in there, you really won't see much of a difference, just some possible tone change in your engine, and maybe a sputter hear and there. But because your engine is tuned for 91, constant driving using undergrade fuel MAY, the KEY WORD IS MAY, cause your engine to detonate incorrectly and cause engine failure. T

t-von

iTrader: (8)

What a typical response form someone who obviously doesn't have any real knowledge about this subject. I bet I have more original miles on my engine than you do young one. With lower grade fuel I might add.

t-von

iTrader: (8)

I understand the cost savings is irrelevant however, the subject matter is whether it is safe or not.

Sgtblue

iTrader: (16)

Well, in my mind, the two are inter-linked. If your running a lower grade fuel on a regular basis, I have to think it's for the cost savings.
To me, it's like smoking. Since not everyone immediately dies from it, for a number of years it's easy to think it's not particularly "unsafe". But then one day, maybe on a particularly cold morning you briefly go WOT to get onto the freeway....

t-von

iTrader: (8)

Very real possibility there however if everything is working perfectly don't underestimate how much leeway a super rich A/F ratio will give you. One of these days I'm going to install a wideband on my stock car just to get some readings.

Sgtblue

iTrader: (16)

I'm sure alot of guys would also be interested in those results if you could post them, I know I would be. And not just because of this particular discussion. I guess I'm just curious.

nopistons94

typical response from someone whos not cheap? yea


noticed I was a little harsh on my wording, so I edited it for you and put a smiley face to smooth it over.