Quote:
Originally Posted by shivaswrath
Why 89/91 --> only hurting your overall performance of the engine.
The engine knocks because of timing . . .
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Do you have
anything that backs up this assertion?
I summarized above all of the information previously posted on the issue. Do possess any additional information I have not included?
The star-up routine of a modern car is very different than when it is running. The possibility the engine may make knocking sounds in the limited circumstance of elevated temperature on start-up indicates only this. Only pinging when driving means anything.
Again, use 91 if it makes you feel better; 89, if you would like to save a bit. Neither compromises the engine in any way.
Amusingly, the difference in power power produced by a modern engine with one step of pump octane is one to two percent; three to six horsepower on a 335. This is meaningless for the driver (no, you are not going to feel this) but critically important for BMW's marketing when publishing engine specifications.
Burn rate is vastly more important for power output differences - and burn rates has nothing to do with octane.
Of course, if anyone has any objective, real information to add - please do.