I just purchased a 2003 Pontiac Grand Am GT and live in NY where it is winter. Since I want the most out of my car for years to come, I want to know what Oil is the BEST to use. I am a volunteer fireman, so when getting a fire call I don't have time to "warm up the car". I have to go into my car in freezing temps, start it up and then put the pedal to the metal right away. When my Fire Pager goes off, lives are at stake whether it be an actual fire or an Ambulance Call for help. What Oil should I use and how often should I change it? Thanks for you help!!!