Hi,I just purchased a 06 Pontiac Grand Prix GXP with the 5.3 V8,the car has 450 miles on it.When should I make the first oil change and what would be the best oil to use?I live in KS so we see temps from the 100's in the summer to below 0 in winter.I will only average about 5 miles a day almost all of it stop and go traffic and short trips.Most of the time not even getting up to full operating temps.I currently use Trop Artic 5W30 on my other cars.Would this be a good choice or would a synthetic like Mobil 1 be better?Thanks for all input!!!!