Originally Posted by ken-x8

If the knock sensor doesn't work, and people running 87 don't hear any knocking, does that mean the 8 really can run on 87? And the premium requirement is just boilerplate from something else, inserted by whoever pasted together the owner's manual?

Ken

Originally Posted by gwilliams6

I have driven easily a million miles in my (street and race) seven rotaries since 1973 including all three generations of RX7 and now a 2008 40th Anniversary edition RX8, so I have been around the block on this octane issue. Yes in an emergency you can put 87 octane in an RX8, BUT you also risk more than just poor engine performance. You also risk transmission issues as smooth shifting and transmission performance is designed for the engine operating at its optimum, as power is sent to the transmission . And any prolonged use of that 87 octane can lead to engine damage. Don't make a big mistake and think you are safe here. The engine has a higher compression ratio than any NA 13B before it, and it needs that minimum 91 octane to keep from detonation etc.

Drive it gingerly, NO REDLINE at all !! And fill with 93 octane as you use up the 87 octane. It will take a couple of tankfuls of premium before you will get your optimum engine performance safely back. If you really push the engine while using 87 octane, you may be in the market for a new engine. It has happened to RX owners before you !! Mazda tells you that you can use 87 octane in an emergency to keep owners from freaking out when they make a mistake at fill up, thinking they can't drive the car at all. I have done it myself, more than once over the years. The RX8 will continue to drive but you are not doing your engine and transmission any favors. If it didnt make any difference, as some would tell you, then Mazda would tell you to use 87 Octane , and save its RX8 owners loads of money. And the ECU will NOT adjust the spark for the lower octane. It will think you put in the minimum 91 octane like you are supposed to have done.

Originally Posted by jasonrxeight

knock on a rotary engine is probably different than on a piston engine because the way the rotary engine works. just because you dont hear it doesnt mean its not there.