I recently bought my RX8 and upon buying the car the dealer told me that 91 octane gas should be used. His explanation was that they have had previous owners use regular gas and their check engines light went on after ~1000 km. Upon asking why that occured he did not have an answer. Big surprise (I have found most dealers know nothing about the renesis and that we are their guinea pigs). I checked out the drivers manual which says regular gas is okay. Now I am really lost. Mazda Canada says use whatever gas, but my dealer says use 91.

Given that gas has become exhorbitantly expensive I figured I would enquire to see if any RX8 owners know whether 91 octane gas is mandatory or not.

 

Use the Search function. This is one of many topics that have been discussed into the ground.

 

as expensive as gas has become, there is actually LESS reason to go with the cheaper stuff.

The % cost for 91 oct is less now than before.

e.g;
If regular is $1.00, and prem is 10 cents more, you're paying 10% additional.

If regular is $2.10, and prem is 10 cents more, you're only paying 4.7% additional for prem.

 

That's an interesting way of seeing it (and justify paying for the premium). I however have to disagree with the idea...

While percentage-wise it is less, it costs and extra 10 cents/Litre no matter how you look at it. $5.00 savings on a 50L fillup is $5.00 regardless of the base price.

Not that it matters... it's still a ripoff. Oh the days of 0.59.

 

Sorry for the digression.

Your answer in short...

YES there are drivers who use 87 or 89 octane. Some say there is an observable improvement in idling and no pinging without degradation of performance. Long-term effects are still to be determined.

Mazda stands firm on 91+ octane.

It's your choice. Your warranty should cover you with which ever octane level you choose.

 

If you look in the manual it says 91 octane reccomended not required. I've used both and see a small performance improvement in the 91 octane, but since I spend 85% of my time commuting, I don't exactly need warp speed. The ECU will detune the engine to suit the octane of the gas to prevent knocking.

 

been using 87 for more then 10k km and i have not had any engine problem whatsoever.

 

I've used 87 for about 8000kms now and yeap, no noticable degradation in performance at all or pinging or anything!

 

Ditto, used 87 for a whole tank now and see no difference, except cost at the gas station :D
________
Justin Bieber Fan

 

I've been using the 87 octane since about March and I haven't noticed any performance loss, in fact I think that it starts better and idles smoother.

 

my experience, i read into all the threads to with a grain of salt, ive tried all the gas types....

i think the car runs best 87-89....

thats it, thats my scientific butt-dyno test...i think the car runs better with regular gas...

 

8000 miles on 87 octane here with no problems.

 

87 runs fine, no problem.

 

I'm a 'by the book' kind of guy. But when I see the above post with the table showing no real difference between octane levels, I start questionning what I read in the owner's manual.

If no engine pingings have been reported and everything looks kosher with fuel consumption, I am starting to become a believer.

I guess that there's no way that it would void the vehicle's warranty if there are any ill effects?

It's like saving 5 buck a pop at the pump.

 

Then you should know that the books says it is okay to use 87 or higher - so how could they void the warranty?

 

Oh?

I don't remember seeing other octane levels are OK. I'll have to flip through it again.