Quote:
Originally Posted by Tork
going off topic with a lack of Texas talk 
I am pretty sure I am getting about +2 MPG with 93 octane, seem to get better with acetone and 87 vs straight 87 as well.
Not a 100% sure, but it looks that way.........
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Around here this weekend regular is $2.49 and premium $2.69 per gallon.
Thats 8% increase in cost. In places its 30c per gallon more, or a 12% penalty. The difference between 32 and 34 mpg is 6%.
When you spend 8% more for gasoline to gain 6% in mpg, that isn't worth the money.
You may notice that premium does have higher heat of combustion than regukar, which is why you get the extra mpg and why premium is needed for on-track activity.
And true premium does burn slower, which is why static timing on premium fueled vehicles are more advanced than regular fuel specifications. But unless those premium fuel specified vehicles (BMW etc) are programmed to advance further unless spark knock is detected no advantage is gained but hp is. . Few cars specifying regular fuel have that programmed simply because the gain in hp isn't important..