Xyntax

I have filled my 3rd and 4th tank with 87 octane now. On my 3rd, I used 87 from Chevron station. On my 4th (current), I used 87 from 76 Station.

BTW, how do you spot when your engine "knocks"? Ever since I had my 8, I always here this "tock" sound in the engine bay while stop at a parking. Finally, I opened the hood and waited for it. To my surprise, it was just the cooling fans activating!

Is there any other way to watch out for a knock? What about from the Tach, does the rpm surge significantly? Please advise.

And last thing... another difference from 91 and 87 is the smell of the exhaust gases. With 91, I always smell unburned fuel. It was like half of the injected fuel just went out without burning at all. With 87, no more funny smells.

Tirxer

my heads about to explode, so confused...

so, should i stick with the 91+ octane that states in the manual OR use the 87 like other fellow rxers???

Xlorn

Wondering how much temperature plays a part in this? In Texas would it make sense to run 87 during the coldest part of the year and 89 during the summer?

rx8cited

Why not try it for yourself? I'm happily running with 87 octane. If you don't like it, switch back.

BTW, the manual states: "You may use a regular unleaded fuel with Octane Rating from 87 to 90 (91 to 95 RON) but this will slightly reduce performance."

rx8cited

Speedofheat

My dealer in (Earnhardt in AZ) has said to run 87. I have since the 2nd tank I have 2000 miles now. And it has run better at idle with no performance difference.

RodsterinFL

WOW this thread is still going! To add to the info, the dealer technician told me to use 87 octane gas when I mentioned occasional idle roughness. I told him I already used it.

Killerking1964

I don't know about your owner's manual, but mine says explicitly that 90 octane is the lowest to run in the 8. It's a high compression engine and it needs the extra octane. Running high octane in a low compression engine will burn hotter and extended use can reduce engine life. In our 8's, though, the performance of the engine will suffer if you use gas w/ an octane of less than 90, and isn't perfornamce why we bought these cars?!?!?

D MENAC 7

Killer...Oh good grief, didn't you read the first 8 pages??, Geeez! I think Mazda didn't really know, still don't what exact Octane rating should be used...it was still a new engine when they wrote it.

Also, they changed the flashed the ECU before import so it would burn a richer mixture to pass future emissions standards and that by suggesting higher octane fuel was a way to ensure it would.

I have yet to put higher than 90 octane in it and it has never run or idled rough, the gas mileage depends on how I drive it, it's never got over 16 MPG yet and there are no pings.

rx8cited

Killerking1964,

Please quote your manual and version - I'm interested in exactly what it says, not your interpretation.

Why is Mazda telling people to use 87 octane if it's bad for the engine? Ummm, they want us to buy a new RX-8 in a few years ...... yeah, that's it .

Many of us are quite happy with the perfomance we get with 87 octane, it's cheaper, in some cases the engines run better than 90+ octane, and Mazda says it's okay to use it. Okay, we know you'll blow us away with your high octane fueled RX-8, but that's alright .

regards,
rx8cited

RX8Z

I checked the manual for you guys, and even contacted our service tech guys, which also own and maintain their own rx8's

They all use 87 octane gas for the reason of Rotary Engine does not reuire a high octane premium fuel

However they use premium fuel once every month or so, to clean up the engine.

From what the say and being one of them is a Rotary expert, I would trust their word. I am also currently using 87 octane and I see no loss of power , and in fact.. I see an increase in mileage..

Good luck guys

z

Tirxer

im trusting your word

racerdave

Ok... this analogy isn't totally spot-on, since we're not talking about a Renesis.

But...

I guy I know who runs well in GT3 on a National level, also runs on a shoestring budget. I'm not sure what he's running now, because there were concerns about passing "fuel tests" with oxygenated fuel.

But... for years he ran his full-on Drummond race motors on 87 octane from the local gas station. Had no problems.

Again... not a Renesis (actually as 12-A), but just showing how a highly-tuned rotary can run on low-octane gas.

FWIW...

RX-jimenez

I been using 93 since i bought my RX, never had a problem, Why i will put cheap stuff in my brand New car?? Is like buying a Brand New house and putting Cheap Paint that will Fade in 3 Months....Now for the experts here, and theres alot of those, 5w-20 oil is the same cheap or expensive? will you put cheap oil in your car just to save a few bucks now and spend alot more later?

bobclevenger

Using higher octane fuel than your engine needs to prevent knock makes about as much sense as offering your car salesman a tip. It's just throwing money away and does not benefit your car one bit. But if it makes you feel good...

Xlorn

Started using 87 octane after I had about 1000 miles on the car. 2 full tanks and no problems. MPG increased from 15.3 to about 17. Maybe a little smoother idle, but that could be my imagination.

MPG seems to be improving as the engine wears in too.

RX8_GT

On my third rotary car since 1985 - always used low octane 87 to 89 gas without performance loss or detonation IMHO. Using high octane in RX-8 at present but considering changing to low octane when car is broken - 5K at least.

Flooded the car once - and one very hard start - shortly after the flood. Driving and starting well now. Hopefully not an ongoing issue.

sferrett

The only reason I use 91 in the rx8 vs. 87 in the other N/A rotary car is the higher compression that the Renesis engine has vs. the standard 13B from my '90 rx7. If it were the same compression ratio I'd be definately using 87. Given that it's not, then I take the recommendation in the owners manual and use 91.

no issues with the car to date.

RX8Z

Thats a horrible analogy. 87 gas does not equate to cheap paint. Please learn what octane levels mean before you corrupt the minds of some of the new owners here.

I didnt suggest putting 87 octane fuel to save money, god knows If I wanted to save money.. Id buy a Hybrid Fuel Cell car.. Saving $$ is just a side benefit of using 87 octane fuel vs 91+

If you use 93, thats fine.. continue it but I can almost guarantee you that your not doing anything to improve the performance, reliability, or mileage with such high octane fuel. Rotary is not a piston engine, it does not work the same and does not need such high level octane.

but as someone stated here, its a mental issue.. you think cuz you put the highest octane, you think ure feeding it Red Bull juice.. Thats the results of great Marketing

Z

RX8Z

Guys,

I also wanted to suggest to you that though I dont think MAzda did this on purpose, but if you notice in general alot of manufacters tend to always suggest higher octane fuels for your car..

I believe Honda, is probably one of the first makers that specifically designed the new primeline models (Accords..) to use regular (87) fuel..

If you compare to Camry, Maxima.. they all want 91+

I think in the eyes of the car manufacters, its an industry mental standard that a buyer would feel their car is "better" because it uses higher gas..

I know this sounds crazy, but im telling you.. it works. Do you know how many times, I tell people.. oh the 6 speed accord coupe, all it needs is 87. and they say" Wow it must be slow then.

After a demo test drive, they realize thats obviously not the case..

Squidward

my cynicism leads me to the following unvalidated, biased, but probably true criticism:

car companies conspire with oil companies to milk consumers

true or not true?

CERAMICSEAL

I don't believe there is conspiracy amongst these groups; obviously they are both about profit. If that were the case for example, they would encourage more oil changes and not suggest that everything is rosey stretching to 7500miles.
The auto manufacturers are often struggling to stay afloat, far less make a profit in this current world economy. They both have their strategies for money making and are influenced by many factors including world and market specific environmental concerns. They must communicate and co-operate; but conspire?

skagen

Umm...my family has had 3 generations of camry's, none of them suggest premium, only regular. As we leave the lot, the dealer even tells us, don't put premium, regular is actually better for camry engines. Honda accord, the new one, I went Honda about a year ago to look at the new two door accord, dealer says regular gas works just fine and so does the sticker.

By the way putting regular gas it doesn't affect performance instantly. The question is whether or not it'll affect your engine in the long run. That's like saying if I eat a Carl's Jr. double bacon cheeseburger today, I'm gonna feel like crap. No, it only happens after years of eating that ****, and you have a heart attack later. Same thing, just cuz you put regular gas a couple of times doesn't mean you feel a performance change right away, it'll take some time for residue build up to take place. The question is, does that happen to a rotary engine with just regular gas?

rx8cited

Exactly ........ show me the scientific evidence ........ otherwise its just hearsay.

murix

I am currently using 89 myself. I was using 91 previously but feel it is overkill as well, especially when the car is blatantly running too rich. Last thing I need is for slower burning petrol. I should probably drop down to 87.

flatso

I was reading an article on using lower then recommended octane and the engine retards the ignition to handle the lower octance hence the reduced performance. However he went on to say if the retarding(?) system should fail you could have major engine damage happen to your car from detonation. I am not sure if this applies to our cars but wanted to offer this info.