You most definitely do not want to have your Toyota Corolla smog checked with 4 to 6 month old gasoline. We highly recommend using up the gas that is now in the gas tank and filling 3/4 full of fresh fuel before the smog check. Having to use fresh fuel will serve two purposes. 1) You will burn out carbon deposits from your engine and exhaust system while driving on the old fuel. We would have recommend driving for a week or two even if you had fresh fuel in your Toyota, since it had been sitting for a long period of time. 2) The fresh fuel which your Toyota Corolla's engine will be running on during the smog test will be much more volatile (than older fuel) and produce cleaner emissions.
