RodsterinFL

I know that the manual says premium as does the fuel door but the manual also mentions the use of a lower grade of fuel. I sthis wise? Did the other rotaries allow for this. I am at work but I think it said 89 octane minimum. Thoughts?

mikeb

use 91

mystrx8

Most of the places around my area only give three choices: 87, 89, or 93. I use 93 and won't use anything else just to be safe.

OmegaBob

Sunoco offers 94

Spin9k

I wonder what rated octane gas all the people who have dynoed their cars used? As Mazda's RX-8 manual says this does lower performance, could that be one thing that effects the HP readings they got?

Not sure if anyone has mentioned that, there are so many posts.

blizz81

I'd hope they wouldn't use anything but premium on the dyno vehicles.

Previous discussion about fuel grade:
http://www.rx8forum.com/showthread.p...t=knock+sensor

After catching the end of that thread (I didnt check back up) I still would side with using premium. The Chevron guy's logic from the quote (among others)...

"The main advantage of premium is that it allows automakers to advertise a few more horsepower by designing and tuning engines to take advantage of premium's anti-knock properties. "

...still kind of says "well, if your engine knocks a tiny bit, it's no big deal" to me. Yes, a knock sensor can keep damage away from a knocking engine, even over periods of time I suppose. But I still wouldn't want to be testing it, partially on the grounds that it enters as another possible electrical cause to performance loss/hesitation issues down the road. I've seen on boards people taking blind stabs at replacing knock sensors, O2 sensors, other sensors, to overcome hesitation once their car ages a bit. Sometimes they report replacing a KS works. What's iffy about it is, ECU codes fail to be the best of guides in problems like this. Head over to some of these boards, maxima.org included, and ask "So it's clean-cut to tell if my knock sensor is going bad and is the cause of my hesitation, right?" and see the responses.

People mentioned about how your normal tank of gas only causes so much on engine knock, and how mazda might be covering themselves for the occasional "bad tank". But remember it's not just gas, it's other factors for knock...ambient temperature, incline, etc being just a couple suggestions.

RodsterinFL

THanks

dcfc3s

Here's the deal -

You want to use the LOWEST possible octane you can WITHOUT KNOCK. The lower the octane, the FASTER the fuel burns. A car that's designed for low octane (like a 1st gen RX-7 or a 2nd gen non-turbo) will run better and make more power on 87 than on 93.

With a high compression ratio or some type of forced induction (turbo or supercharger), you need a slower burning fuel to overcome detonation due to increased combustion chamber temperatures. Ergo, higher octane.

Yes, you can run the '8 on lower octane. I would ONLY do that if you're in the middle of BFE and all the pump has is 87. But, I would drive it nice and easy until you can get some higher octane gas.

By the same token, ALWAYS get gas from a name-brand station - Texaco, Chevron, Citgo, etc. Don't buy Circle K gas or mom-n-pop gas! There is a quality difference. I had a buddy gas up his car at a Circle K and thought something was broken on the car the gas was so bad.

Good quality gas also has additives to help clean the fuel injectors - VERY important. The secondary fuel injectors on RX-7's have tendencies to get gummed up from disuse - yet another reason to romp on your RX-8 every now and again.

Dale

Doctorr

One more point about gas stations,

NEVER refuel when the gas delivery tanker is around......

If it's just pulling into the station, it means the tanks are low, and you are getting the stuff at the bottom, and that includes any rusty water that settles there.

If the truck is filling or pulling out, you will definitely be served stirred up rust and water, it needs at least an hour to settle.....

The industry calls this 'BS&W', for 'bottom standings and water'.
It is there, we measure it, and note it is not just called 'water', often what is down there is chemicals that have settled out, amines, caustic soda, merox catalyst, etc. Trust me on this - whatever is at the bottom is best left there!
.
.
.
doc

Genom

Wow. Thanks for that last tip. I did now know that and had never heard about it. Save my engine! SAVE MY ENGINE!

Sorry. Just that yesterday as I was putting in some gas (just a little 10 buck stop) they had the delivery truck there. Dunno if it had just started or finished but sounds like it doesnt matter.

Wing

Ok just wondering. Everywhere / everyone states you should put the 91 octane in a car with high compression.

So our engine's compression ratio is 10.0:1 But I have done a little research and notice there is many other cars with this same ratio that call for regular 87 octane?

I just looked for curiousity at my previous car (Hyundai tiburon) compression ratio 10.1:1 fuel type regular.

So is there something else besides compession ratio that require us to use premium?

sleeepyhead

here it states that all NA rotaries recommend the lowest octane. This was probably written before the rx8 came out but it says even highly moddified NA rotaries should use 87 http://members.ij.net/mrmazda/cfaqtext.html#ROCTANE

Wing

Now THAT is interesting...... hmmmm so better fuel mileage and cheaper gas? Man this is ODD that they recommened premium.

Are they just recommending premium to save their butts? Just like all the other things in the manual? Are they recommending it because sports cars should use premium and if they say regular more people will think it can't be a sports car?

Hmmmm.

8thSin

I originally posted the 13 mpg post.. and recently have filled up at Chevron, using 89, and have seen a better consumption of gas.. currently about 60 to the 1/4 tank, with about 40% hard driving.. Don't know if it is the Chevron, or the 89.. will fill up again with 91, and see what I get.

Wing

Keep us posted, I'm thinking of trying 89 as well, actually sunoco is 89.5 that's CLOSE to 91

RodsterinFL

Wow, what a controversy. This is great stuff here - just what forums are for.

I noticed that the manual (I looked again) says we can use unleaded regular 87 octane but with reduced performance. So basically we apparently can use any grade - 87 / 89 / 91.

I have been wondering about this since I too have a lot of soot at the exaust and when I start it in the morning it misses. I know that 2 cycle engines dislike the high additive mid and upper octanes and wondered if possibly the addititives were causing the soot.

Wing

Yeah, I get a lot of soot too and it misses BIG time in the morning. That's it next tank is REGULAR! We'll see how it goes.

If I suddently get 30mpg I'll freak at the $150 I spent for gas now that I have 1000Km on my car, it's be crazy expensive!

TJRX8

I tried a tank of 89 and it had a constant slight ping. Took me awhile to figure out what the noise was. Filled up with 93 and it is gone.
So much for using the cheaper gas.

Wing

Hmmm, I'll try 89.5 when I have to fill up again. I just read the manual as well.

Says, You may use any regular unleaded Fuel that is rated 87-90 octane, but with a slight reduction in performance. Anything below 87 could cause damage to the engine.