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Am I using the wrong fuel?


grayfox2
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i have been using 87 in mine and don't notice a problems. If i am going on a long road trip (more than a tank) i will sometimes put in a tank of high test. I don't notice much of a difference in performance, but i do get a bit better mileage

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the factory handbook actually says not to run anything over 87 octane.......... before i knew that i ran 89 and mini would ping...... run 87 and all happy again. the 91 octane can actually harm your engine over time if it wasn't built for that type of fuel in the first place (like a corvette/sports cars/yadda yadda)

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with 15 deg spark timing (instead of 12) and headders I notice a benifit in mpg from running 91 octane. On my tirp to cali last week I got 18.5 mpg carrying 2 passengers, a dog, luggage, lots of holliay gifts for the family, 100lbs of snow & recovery chains, and full size spare on the back. I only used 91 the whole time.

Normally I use 91 every other fill (I normally fill @ 1/4 tank) and get pretty decent mileage.

 

the problem with using too hig octane is that it does not ignite as fast. Ideally when the spark hits it, it does not combust undill the downstroke has just started. too high octane and the "flame front" has to catch up to the piston before it can push it and in worst case not finish expanding before the piston starts going up again...

Edited by MY1PATH
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oh, and timing is SUPPOSED to be at 15 degrees (i run both mine at 14 tho)....... if you had your timing at 12 degrees, and lived here in CA you'd fail a smog test.

the TBI engine specs call for 12 degrees and the MPFI calls for 15 degrees.

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