Quote:
Originally Posted by aerohead
theunchosen,I dug out my old text and it basically concurs with everything you've posted.There were over a dozen pages which dealt with "autoignition" which the text suggests is present in all "real" engines,from sub-audible high-frequencies,to the destructive "severe" detonation at the extreme end of the spectrum,where impulses from supersonic pressure pulses create stresses on the engine structure,enough to cause failure.---------- My thought,with respect to hummingbird's situation,was that if all other variables were held constant,that the lower octane fuel would prevent maximum timing advance,forcing the engine to operate at a lower efficiency,leading to the lower mpg.
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I can agree with that. I don't think I ever disagreed with you on that. I think I just got over excited and wanted to tweak something just a little.
I'm not certain about the italics part. actually I agree. But with respect to overall savings I think the engine is definitely smart enough to avoid damaging itself and just run at lower hp output and get slightly less mpg, but in the long run cost less(premium here is I think 30 odd cents more than regular). Its hard to estimate this though without several tanks using premmy and several tanks using regular with maybe 3 tanks of one and then 3 of the other in succession to make sure the premmy fluid clears the 2-3 tank to get good results for the test.
My inclination is always to go with the cheapest possible fuel if it doesn't hurt the engine(or radically reduce FE), but I don't have all the data or maybe even enough data to get a feel for that(seasonal changes in op case).