Just got stationed in WA state. All i have is 92oct. Should i use the 93 oct or 91 oct on my SCT X4?
Thanks,

 

91, never use a higher tune than the octane fuel in the tank.
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Wait!!

You mean you have 93 octane rating gas and a 92 octane tune?

 

Sorry. After re reading my question i realized how confusing that sounded. I meant to say the only fuel we have up here is 92 octane. So, should i select the 91oct tune or 93oct tune on my SCT X4?
Thanks,

 

91 tune.

 

Thanks brother!

 

91 as Perry said. You could get detonation if you run 93

I dont know if the SCT X4 adds timing when you up the octane, but if it does, you can do some real damage.

 

Is there such a thing as too high octane for the tune??
Came across this thread and I'm learning something...thanks guys

 

The only thing that will happen with a significant octane abundance is a reduction in power output due to peak cylinder pressure occurring later than optimum. This happens because higher octane fuels burn slower. A by-product of this slow/late burn is somewhat elevated cylinder head and exhaust valve temps., although not enough to cause any damage. Bear in mind that I'm talking about an excess of 10 points or more. Two points is absolutely insignificant. Ten points is something we have to deal with in aviation. All avgas is 100 octane which is fine for high compression /turbocharged /supercharged engines, but our smaller low compression engines were all designed for 87 octane, which is long gone. The only thing we can do to make up for this is bump the timing up a couple degrees (3 is about right ). I, of course, would never do this as it violates regulations

 

Thank you sir!!!
It takes me a month to burn through a tank of gas ( on average...36 gallon tank) I haven't changed tunes yet, still running 87 p/t. I also have 91p/t and e85 performance. And was thinking I should work up to e85 after running the 91 and not go from 87 to e85.. or am I over think'n this??