I have been getting horrible gas mileage the last 2-3 days and I couldn't exactly figure out why. So I checked the oil and rad. fluid and both were half way. I know to put mobile oil in it but what is the best brand antifreeze to put in, seeing as I live near the cold Windy City (Chicago). Thanks!

Just make sure the coolant you choose is a GM Dexcool type. It should have a red or orange/red color. Do not use the yellow stuff. Also make sure you mix 50/50 with water and add until full.

I have a question that bothers me more. That question is why is both your oil and coolant levels half way full? There has to be something more serious going on than just loss of oil or coolant over time. I'd suggest having it looked at if you are under warranty still. Let us know how it goes. I'll let others recommend their preferred brand of coolant. :)

I'm suspecting she's been driving the car since new, and has done little or no maintenance.

Miss GTO, I am ORDERING YOU to take your car in and have it serviced.