I have noticed that since it is getting colder outside my fuel mileage is not doing so well. I have dropped about 2mpg in the last few weeks. Is that because of the grade of the gas they are now selling or do I need to take it back to the dealer to get it checked out?

 

No, usually the fuel mixture is enhanced to promote faster warmup periods in vehicles during the winter months. The end result of this change is less efficient burn charactaristics of fuels.

My twin turbo Stealth usually got around 20mpg no matter how I drove it in the summer months. Now with the winter grade fuels, I am hitting about 12. Ugh... premium fuel + 12mpg = unhappy wallet.

 

My mpgs dropped too... not happy lol.

 

Colder and drier more dense air cause the fuel/air mixture to richen up and therefore you will get less fuel economy in the winter.

 

And the fact that ethanol is added as well...this equals less mpg.

 

Yes, I agree and as the OP alluded to also and why I didn't mention it.

 

Alcohol is horrible for gas milage, not near as good as just good gas but it is cheaper and the gas companies would go above the 10% if they could