zerobanger

Just curious...

The owners manual said that 91 is prefered for best performance but if you use 87 octain there will be a minor performance decrease. I didn't see anywhere that it said it REQUIRES 91.

So can 87 be used? I'm just curious if it can be and if there is any noticeable difference.

RX-GR8

some people have used 87 and 89 octane and have reported slightly better MPG.

9-K Rever

I will tell you my 87 octane horror storey.

My gas light came on and I didn't have the luxury of being picky with my gas stations. So I hit the closest one, wich happed to be a CITGO... I have had my 8 for 6 months, with nothing less then 93 octane in it the whole time.

So, I put my card in the pumping station, hit the 93 octane button and started to fill up. But, something told me to look at the pump, and when I did, I was like, why is this so cheap.. ? So I got out of the car pulled the pump and got my recipt, and it said 87 octane..

I was like oh sh*t...

So, I turned the car on and it started up normaly, and I decided to drive it home under low RPMs. That was fine...

But, the next day, when I started the car it barely turned over and when it did it the exhaust was just sputtering and poping..

The idle was uneaven...

So, I finaly drove it down to a half a tank and then filled up with 93. So, its been fine since I did that.

But, from that experience I will never put anything less then 93 in my 8.

9-K Rever

TheDosDog

In 3000 miles I have run 87, 89 and 91 octane. I haven't noticed any significant difference. This may not hold true though in warmer months. Since my MPG (maybe MP$) seems worse on 91, I usually go with 89.

8_wannabe

Other than about 4 tankfuls, I've used 87 exclusively. No problems. No detectable change in performance. No sputtering. Re: 9-K Rever's story about CITGO, is probably due to dirty gas, not due to low octane. If the octane disagrees with your car you will get knocking. Then you need to move up to 89 or higher. If you don't get knocking, all you are giving up is a few horsepower in performance.

9-K Rever

You may have a point, I never use CITGO gas...

I may put some cheap gas in my 8 from time to time..but, its never Citgo and never have I had such a bad reaction.

So, it was enough to scare me of of 87...

My engine's pitch even changed. I listen to it all the time, and when it spins up and down it has a specific pitch....and with the 87 it was like a drowning sound...

Very discouncerting..

9-K Rever

DMRH

Back in the 70's, Curtis Wright did testing on compression levels with there RC2-60 engines.

RC= rotary combustion - 2= 2rotor - 60= 60ci

They did testing from as low as 83octane to over 100octane.

There documented testing proved that the engines performned normally under all fuels. Power wise, there was about a 3 hp difference.

As the rotary engine burns its fuel in a different manner compared to a piston. Its not as susceptable to octane levels as a piston. This testing would have killed a piston engine but the rotary prevailed.

While an atmo rotary will show no effects between 87 & 93 you start to notice octane ratings with a turbo rotary when its compression is artificially increased.

Although my HC3S Luce runs 87 on its 13B turbo using 8psi. My JCES Cosmo uses 93 as I am running 15psi boost. I will say that its 20B engine has "pinged" with 87 running that 15 pounds.

So the (proven) moral is that higher ocatne fuel in an atmo rotary only effects the wallet.

i3man

I've used 87 and 92 with no noticeable difference. I'll try 89 next tank.

Rotary Nut

When I had a tank of 87 in my 8 it was okay untill I floored it trying to pass a ricer . It sounded like someone throwing marbles at the windshield at around 6000 rpm. Never again!

Zoom2X

I have used 87 and did notice that performance suffered a little under hard acceleration. I have no problems at all with 89 so I usually use that for normal driving, it has less impact on the wallet. If I'm going to on a road trip where I know there are long hills and/or high temps (like going to Las Vegas) I use 91.

zerobanger

WEll I filled up today for the 2nd time since I bought my car. My first time I got 15 Mpg, This time I got 17. I dont consider this bad as I have been varying the load on the engine running from 2500 to 5500 rpm or so.

I just filled up with 87 octain and drove home. I dont notice any difference yet.

KFence27

I've noticed a power difference in using 87, i now stick with 93 everywhere and always. Its only about a 100$ a year difference and worth it if you ask me.

Rick

Me too. I wonder if the 4 port A/T is more likely to knock using 87 octane than the 6 port M/T

S3/P3/E2

Running 89 right now with no complaints. I can afford the 93 without thinking twice (my 3000GT HAD to have it ), but I'm splitting the difference between the choices right now. So far so good.

captainrx8

I burnt 93 i my Jag XK8 (last car). Might as well pamper the 8. Nothing but the best 93.
Jeff

Speed_racer

Correct me if I am wrong, but I read somewhere that the computer in fuel injected cars adjusts to the octane in the gas.

So if you are using 93 octane all the time and you suddenly switch to 87 octane, the car may ping for a while but after a few tank fulls the computer will adjust the amount of oxygen ratio so the pinging goes away.

Anyone else heard of this theory?

Rick

If the knock sensor detects knock the ECU will adjust the timing. I don't know about the fuel ratio. I do know that I heard knock a few times from seperate fills of 87 octane.

Ole Spiff

I've been running 87 octane for months now and the car is performing beautifully; no knock and it feels quicker than when I bought it. There must be something different in east coast gas or cold climate gas because here in southern Cal we don't get the severe reactions I read about some of you getting in cold areas; especially back east.

I'll be switching back to 91 octane as soon as Canzoomer's Stage 1 kit arrives and I get it installed because it requires it, otherwise I'd continue using 87.

Ole Spiff

Oh and I forgot to mention that it's important to get quality gas; not the cheapest, watered-down crud you can find. I tested all brands available in my area and got the best results with Shell gas; second best with Chevron. I use Shell 87 regular exclusively now.

Speed_racer

You are absolutely right about that OLE.

Stay away from Citgo. Shell and Exxon are good.

trinity77

I've used 87 and 93. Notice a bit better performance with the 93.

I've been using Quicktrip with no problems - I think you need to find a station that is dependable and go there. Even Shell can be bad - happened to me with my Jeep - got a bad fill-up at a Shell station away from my house - had water in it and couldn't start it the next day!

sferrett

It's also a bad idea to compare the 13B rotary with the Renesis rotary when talking about fuel octane. The Renesis has higher compression and so is more susceptible to knock than the 13B of the rx-7 cars. I run 87 in my non-turbo rx-7 and 91 in the rx-8 - peoples description of knock when using 87 is enough of a warning to me not to try it.

9-K Rever

I am glad you brought that up. It was ironic because I gave a nice little lecture on my thread about dentonation and 87 octane and then I put 87 in my car.

But, the point I was wanted to make on this thread is, that the 87 went in by ACCIDENT. Not on purpose...that was the scarey thing. I hit the 93 octane button. Boooooooy was I upset.

If you want to read my lecture here is the link. But, what I said should be common knoledge to the old rotary heads out there.

Keep in mind, like other 8 owners I am still learning about this engine so feel free to add something that I missed to further our learning procces.

https://www.rx8club.com/showthread.p...5&pagenumber=8

9-K Rever

zerobanger

used a 1/2 tank of 87 octain, no problems yet.