The ECM adjusts the timing based on historical signals it receives from the knock sensor and sets a baseline advance curve, mantaining a conservative buffer between that baseline curve and the point at which knocking occurs. Of course, using higher octane reduces the tendency to detonate, thus allowing a more agressive advance curve (hence more power). The ECM will discover this reduced knock tendancy over time and will shift the curve to take advantage of that, but while still maintaining that conservative buffer. What the higher octane tune does is 1) minimize that safety buffer and 2) preset the advance to that more agressive curve.

 

The manual does in fact tell you not to use premium as it can damage the engine.

 

My manual does in fact state
I read this as "if you want to try premium you may experience these problems, so we don't recommend it"

I do also see that after market products "may cause damage to the fuel system", fuel containing methanol "can damage critical fuel system components" and that leaded fuels "could damage your engine", however I see nothing about octane-related engine damage. EDIT: That is, unless you count the section that recommends avoiding gasolines with octane counts lower than 87 in high altitude areas.

 

true - it does not say it will damage the engine (my appologies), however the problems as listed can't be good. I have read this though concerning other engines - such as my Jeep V6.

 

Good point - that hesitation would drive me nuts! Thanks for getting me to think a little harder about it. Hopefully these things are fairly anomolous...

 

for the amount of money it will cost you to fill a tank with premium its not even worth it..you wont get any real gain out of it

 

I disagree. hmmm...87 octane (ok) 91 octane (o yeah - there's the power boost).

 

I am also of the opinion that higher octane will help performance. I have the xcal tuner which is programmed for 3 different octanes. Along these same lines, what about octane boosters? The highest gas I can get is 91 and my third tune is for 93. Are boosters ok or should I just stick with 91? Jim

 

ran boster in my sand rail it messed up the inside of the carbs so be carefull how you use it