Ive heard so many answer to what octane is best stock 89 rx7 n/a with 1000mi on the new rebuild.the pluses and minuses of 87,89,91, or 100 octane who has the real answer

 

All FCs are rated for 87 octane stock. It is in the owner's manuals. There is zero benefit to using higher octane (knock resistance rating) on your NA.

 

The higher octane resists pre det slightly better, but that only really comes into play when ur extensivly modded. Zero benifit for a stock or mildly modded car, well except for a lighter wallet.

 

From the US Federal Trade Commission:
http://www.ftc.gov/bcp/edu/pubs/cons...tos/aut12.shtm

If you want clean burning, then use Top Tier fuel:
http://www.toptiergas.com/

The 100 octane fuel that you mentioned is racing fuel of some sort, and may have a higher energy content. However, you would need to ask the vendor for the statistics because sometimes the octane rating is raised with junk additives like alcohol rather than the good stuff like aromatics.

 

Run the octane that your car is tuned for.

 

He said it was "stock" and NA...so no tuning. 87 should be fine.

 

I run 93 in all of my "performance" cars. For the difference between regular and premium, in PA, it's really not a big deal.

 

ive put some 110 in my car that i had left over from my dirt bike. i have an na 1987 and it smelled good but that was about it.

 

How about you give me some money if it's really not a big deal?

Let's see, average mileage is about 10,000 miles/year, and your performance cars probably get about 20 mpg, and 93 octane is at least $.20 more than 87, so 10,000mi/20mpg = 500gal/year * $.20 = $100. OK, so send me $75 every year and you can pocket the $25, and that way we both come out ahead.

In fact, everybody who reads this thread should send me $75/year for helping them not waste their money. Well, at least the ones who think that wasting money is really not a big deal. Wow, pretty soon I will be as rich as the big oil executives who have been ripping off unknowing "performance" car owners for decades!

 

91 or 93 would always be the best for any high performance motor

 

What makes you think that?

 

The rumor-mill I'd guess. He's just boosting his post count like half the people in here are doing.

It's not a complicated issue, but so many people get fixated on the larger number, and then assume that more = better. Octane != power (!= is "does not equal" for those not familiar with it).

 

As many have already posted the octane of fuel that you use will depend on the tune and timing advance on your car. If you are running a stock car with a stock base timing and compression then 87 is best for your car as 89 and 91 are only to reduce preignition "detonation" or as some people like to call it engine "knock". It is a result of the gas being so far compressed that that alone can ignite the fuel. Sort of like a diesel works. This can be very bad for your engine and some people like to push their limits by advancing timing for a performance gain. Granted you can get a few free hp by doing this, it can be dangerous if you do not know what you are doing. Subsequently, you must then run a higher octane fuel to prevent the detonation from occurring as with more timing advance the more likely your car is to knock. Cheers and good luck!