went from high 20s to low 20s with no change in driving, road conditions etc. what could it be? tuned up 30k miles ago. thanks.

 

Check for gas leaks.

 

alot of people complain about poor gas mileage during the winter. this may be caused by multiple reason. cold weather, gas quality, also check your tire pressure. but if your really concerned take it to the shop. in some states DEQ is free, and if their is something wrong your vehicle will not pass DEQ.