Originally Posted by BackStreet
Winter Fuel is 10% Ethanol, 20% Butane, 70% Gasoline
So you should expect an 8% decrease in fuel mileage vs pure gasoline or 4% decrease vs E10 (which itself is 4% below pure gasoline).
Obviously, other things effect fuel mileage.
Thanks for posting this. I was unaware that much % butane goes into winter gasoline and this explains a few things to me.
The vapor pressure with warming butane may explain a transitory EVAP error code that crops up on my gen-1 car: sometimes occurring only in early springtime when temperatures get warmer.
This also may explain why the OBDIIC&C Gauge A/F parameter reads a value for stoichiometric ratio of only 14.3:1 vs. 14.7:1. [the MTBE, EtOh; C4H10, etc.]
fwiw: info indicates that the amount of oxygen contribution to winter fuel blend ranges up to 28% in some blends.