More nubie questions. Does it matter the octane level of gas used. The manual does not suggest you have to use the most expensive premium, but I have heard others suggest this makes an important difference. Any opinions? Thanks.

 

Use the highest octane...much better

 

No, do not use "the highest" octane. Considering some places sell high octane fuels depending on your geographical location, that is not intelligent advice (shocking...).

In some cases, people are able to use 89 octane without any issue (those being knocking and loss of power), however, it is recommended to use 93 octane if available.

 

93 at a minimum for myself, we are literally talking about 4 bucks per fill up between 87. If you cant spend the extra 4 bucks then you have no business owning this car

 

A better and more efficient way to find out is use this method.

 

Damn, I fell for it again. Clicking on that "lmgtfy" link!

 

Thanks all for the opinion and the instructional link.

 

You just don't like everything i say...i know you hate me, but i like people hating me because that will make me more aggressive and will not stop posting...

 

Shouldn't you take his hating you as a complement?

FWIW, what Mazda recommends is 91, not 93. Higher than 91 doesn't do you any good. Lower causes the ECU to retard the timing to compensate. Up to some year Mazda said less than 91 was OK but gave less perforance. After some year they said more dire words against it.

I use 93 because stations around here have 87-89-93 and I'm not enough of a cheapskate to fill 50/50 with 89 and 93.

Ken

 

Yeah, that too...

 

I'm surprised this question still comes up...

 

Thanks for this insight.

 

I have been running 87 Octane for last 8 months.. 93 octane fill up once a month..Considering the fact my 8 goes through 8 fill ups a month. One of the Mazda tech told me, as long as u run her hard and clear out the carbon you will be just fine.. Just last month I started premixing with Idemitsu, I cant really tell a diffrece though..I hope this helps

 

Compression in the combustion chamber increases the temperature of the air/fuel charge.

Octane is the resistance to auto-ignition by increasing the ignition temperature of the gasoline.

Higher octane means you can compress the air/fuel charge more before it auto-ignites (detonates).

Detonation is critically dangerous to all engines (just most engines are designed to run just fine on 87 octane and thus have no detonation problem)

Engines that are designed for higher octane can only safely run on lower octane through the ECU pulling timing (killing mileage and power) OR if the engine is losing compression.

A perfectly healthy Renesis that has good compression on all 6 rotor faces can not safely run on 87 octane. The ECU can manage to deal with 89 octane, but you will notice performance differences.

A Renesis can only run on 87 octane once it's compression has fallen far enough on all 6 faces. If you have bad compression on 5 faces and great compression on 1 face, 87 octane can still destroy the engine by detonation on that 1 face, shattering seals which shred everything else on that rotor.


Anyone that insists that their RX-8 can run on 87 octane just fine has a weak motor and just doesn't realize it.

Yes, we have seen people come on here with blown engines because the dealer that sold them the car put 87 octane in it.

 

Assuming the higher octane is .30 more than the lower octane, you save a measly $4.80 over 16 gallons of fuel. Is it really worth it to risk your engine over basically $5.00? Most people don't even fill up when they go to the service station making the savings even less.

 

In my area, they are charging .15 to .20 cents extra for each jump in grades. Premium can easily be 40 cents more than Regular.

 

Thanks RIWWP That makes sense.. I will get my compression test done this weekend and compare it with the previous one to find what state is my engine in at the moment and take care of it accordingly. if its still in good order (keeping my fingers crossed) i will switch back to 91 octane, and if its not so good then i will bugg you guys again for tips to help me slow down the damage :-).. Thanks though that was very direct and informative post, cleared out the myths and confusions I had regarding diffrent grades of gas and our car being a Mazda and not a porche :-)