it burn a little more gas than usally why is that on 2005 Buick LaCrosse

every time iput gas in it

2 answers
Winter gas contains ethanol. Ethanol has a lower flash point and less energy per gallon. Gas mileage goes down approx. 10%. That MIGHT be what you are seeing. Does it go back up in the summer?
Do you have a check engine light or any other warning lights on?