Quote:
Originally Posted by longshot270
Jack's got a good point. But I have also noticed that my truck runs different when they make the switch. I also remember Bill recommending to someone who was having trouble to run 91 tune even though there was 87 in the tank. Maybe they mix the winter stuff to resemble the higher grade fuels.
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The "switch" though, comes ahead of the really cold temps for most of us. I still maintain that because of the increased density of the cold fuel, that you are getting more energy out of it per injector shot (which controls volume only) than you do at warmer temperatures, even though it's a "winter blend".
Here in Tucson, they used to blend in MTB? (or something like that) to reduce the Carbon Monoxide (CO) emissions in the winter. Yes, it seemed to hurt mileage. I don't think they use that stuff anymore, since they found it had a cancer causing link, but they DO "oxygenate" the fuel with some additive.
I don't think Bill was saying they actually blend winter fuels to resemble higher octane stuff, I think he just said that the colder overall temps reduced the volatility, which is really what octane is all about (how easily the fuel will "flash ignite"). High octane fuel is simply less "explosive", as is "cold" gas.
Oh, and BlackSTX - GOOD post on winter traction! We don't want any of our members ending up nose into a tree!
- Jack