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300x on 87 octane

Old 08-07-2011, 01:54 PM
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Originally Posted by rsess View Post
My marina is threatening to stop selling 91 octane this year. I know that the 275 Verado and some of the Mercury Racing I/O's (new HP 850 at least) can be operated on 87. A knock sensor retards the timing or something and the power is reduced. Is this the case with the 300x.
300X + 87 octane = BANG, BOOM, SEE YA!

Originally Posted by Tantrum View Post
I am also running 300x's and have a concern that 91+ is going to be hard to find in one of the area's I boat. Im under the belief that 89 is out of the question.
Is this TK-7 stuff safe to keep on board or is it highly flammable. I would be interested in keeping a few gallons on board to add if the fuel I was putting in was questionable.
The 300XS also requires 91. Using 87 may result in a smaller BANG, BOOM, SEE YA.

You can do you own blend.

1 gal 87 + 1 gal 93 = 2 gal 90
1 gal 89 + 1 gal 93 = 2 gal 91

You can also use a good octane booster. Remember octane rating is not a measure of the energy/power in the fuel, it is just how compressible it is.

I should note, that some vendors will put a different mix of additives in various octane rating gasolines, and some additives can promote better/longer engine life.
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Old 08-07-2011, 03:12 PM
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Octane is the resistance to burn not compression, never seen an octane test that compresses the fuel. Preignition or detonation is the fuel lighting off too early higher compression and temperatures require a higher resistance to ignition to slow down the burn rate
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