How often Do you need to add freon to your car?

Only after you have put a set of gauges on the a/c system to read both the high and low side pressure readings then you can determine if you need to add freon and oil to the system. If you just add freon and oil because the a/c system is not as cold as it once was it could still be full but might have something else wrong with it. The one thing that you don't want to do is buy one of the do it yourself kits and overcharge the system, this could lead to an expensive repair due to overcharging the a/c system..........