what octane?

[dascro]

I have a stock 300ex and have always used the cheapest 87 octane I can find. I've noticed that higher octane seems to be popular on here and I'm wondering why, and is there any reason I should use higher octane.

[FoxMxRiders]

I use 92 octane in my 400,the octane delay the point that the gaz ignite on the compression stroke.Because the compression stroke release a lot of heat and if you have a compression that is over 11:1 you will need racing fuel cuz the gaz will ignite before the end of the compression stroke (pre-detonation)

[dascro]

So if I removed my airbox lid and am perhaps running slightly lean, moving to 92 octane should correct the problem?

[bwamos]

Nope. Octane won't help lean/rich ratios at all.

It only keep's your engine from pre-detonating. The high octane will make it ping less when you lean.. but that's just hiding the problem (being lean). It still runs just as hot.. and will destroy your engine.

If your a little lean just put in a main jet 1-2 sizes larger.

A stock 300ex runs at something like 9.8:1 compression (I forget what the actual number is), so regular unleaded pump will work just fine.

If your 10.5:1 => 12:1 you want to run premium pump.

[Punk'd]

I use 92 here for my 450.