Matt Mc_Carthy wrote in a message to TOM WALKER:

 MM>>You _might_.  Modern engines have anti-knock sensors built into 
 MM>>the engine block to 'listen' for detonation and retard the spark 
 MM>>timing accordingly.  I by using a higher octane fuel the anti-knock 
 MM>>sensor fails to 'hear' detonati then your onboard computer may let 
 MM>>the engine run at a higher timing advance which would improve your 
 MM>>mileage.  Even one or two degrees additional timing advance should 
 MM>>give you improved mileage in the range you seek.

 TW>  ONLY if there was some problem with the Engine itslef. Like bad 
 TW> timing

 MMC> I don't think so.  Most car timing is now completely automated,
 MMC> and is set by the computer to two degrees below the 'knock point',
 MMC> where ever that happens to be.  A higher octane will then raise
 MMC> the 'knock point', and thus the timing will run more advanced.

One wonders how often the computer would adjust this...

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