i am new to the site and have found alot of useful info here i would like to thank everyone for the info that you have given me so far and i have another question,my wifes tahoe is approaching 10000 miles and my silverado has 3600 miles on it,she drives 3 miles to work 3 miles home a total of 6 miles a day the tahoe is an 03 5.4 my truck also a 03 6.0 very seldom gets driven maybe up town to get something but waiting to get a camper later this year and will be towing some my question is i was thinking about changeing them both over to mobil 1 5w30 and useing ac filter is it to soon? is the mileage to low for syn oil and is the oil mobil, and filter ac, ok and the oil weight ok or do i need to go with a heavier weight and last how many miles between oil changes thanks