Most standard vehicles on the road today will use whats called R134a which is a synthetic refrigerant which is not damaging to the atmosphere. You can find this at most auto repair/parts store, or most repair shops can do this for you.
In general, two types of refrigerators are used. One is R-12, which was used in older vehicles. Another one is R134a, which is used in newer vehicles. R134a is safer than R-12.
