So I was filling up the car at the gas station, I noticed a sticker on the pump reading "From Nov -Feb the gas will be oxygenated to reduce carbon monoxide" or something along those lines.

Has anyone done a study to see how this affects our tune and performances?

 

might have been the culprit here:

https://www.evolutionm.net/forums/sh...d.php?t=308232

 

My gas mileage on my Eclipse GSX used to go down about 10% when they switched over to the winter mix.