Ok so today I went to the local store and on my way home like a five min drive the temp on the car was going up. I heard if your car over heats ur suppose to put the heater on full blast so I did but then the heater was blowing cold air the ac was not on so I don't get why that happened. Can it just be an oil change? I am due for one and if that's all I need then perfect but what els could cause that problem? I'm just glad it happened when I was in town the weather has been cold and rainy so not sure if that might be a problem? Also my oil life says 40% which I thought my oil was good till 30 how reliable is the oil life reading and what does it really measure?