Most cars should be able to get a 20 deg F temperature drop.
Do this:
Check the temperature in the car.
Start the engine, turn on the AC full. Check the air temperature at a vent.
The temperature at the vent should be about 20 deg lower then the temp in the car.
Do this:
Check the temperature in the car.
Start the engine, turn on the AC full. Check the air temperature at a vent.
The temperature at the vent should be about 20 deg lower then the temp in the car.