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Old 06-11-2013, 03:33 PM
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highlandchef highlandchef is offline
Conventional Eccentric
 
Join Date: May 2011
Location: New York
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Quote:
Originally Posted by huntergreen View Post
do you see a difference between the two?
Quote:
Originally Posted by Hermes1 View Post
I am curious as well. My last vehicle specified 87 octane, except when towing or carrying heavy loads where it specified 91 octane. Under normal driving conditions it performed well with 87, but the one time I towed with 87 it was sluggish. With 91 it performed better.
Around town I haven't seen a difference in performance or mpg (either perceived or empirical) which is why I run 87. Granted I'm fairly easy on the right pedal in town so there might be a different result if you'e driving style is different than mine. On the highway, and particularly when towing, IMHO, there seems to be a perceptible difference in performance with the 89. On tanks I judge as truly 89 vs 87 (in other words not mixed) I believe the truck runs better. I also find slightly better gas mileage from the 89 when towing. From my log it ends up around 1/2 mile per gallon. Not much and definitely within a possible error, but the difference is consistent over time.

The exception to the above is when I've been able to find real gas (no ethanol). Even at 87 octane the truck runs better and the mpg increase over the either the usual E10 at 87 or 89.
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