Quote:
Originally Posted by B440
Two and three are backwards; The older engines will run leaner if they cannot adjust a/f ratios, and possibly better mpg at the risk of engine damage. Newer cars that can adjust, will add more fuel because of the alcohol, lowering mpg.
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Sorry, but the ECM in almost ALL of the
newer engines, especially those using turbochargers, actually "test" the octane levels of the gasoline by periodically "advancing & retarding" the spark ignition, using the principle that E10 (and higher) mixtures have higher octane levels due to ethanols higher octane number (100+) than 'straight' gasoline. Typically, this process is done upon each tank refill, and then more often as the car is driven.
How do I know this? Because that's exactly how our 2011 1.4LT Cruze works, and because I can SEE it occuring with my ScangaugeII™ when different mixtures of E10 and E0 are used. I see advanced timing consistently with E10+ fuel, but timing retard consistently with E0 fuel.
Similar process happens with Ford and Fiat-Co (pronounced fiasco) cars with turbos.