Of our 3 family cars, mine ( 3800 Series II in a 2001 Buick) is the only one that requires 10W-30 for warm weather conditions. The others use 5W-30 24/7/365.
Of course, since I live in New England, the term "warm weather" is relative , to say the least. I just changed-out my oil to 5W-30 now that "the frost is on the pumpkin". Could I safely get away with running 5w-30 in Spring, Fall, and Mud Season as well as in Winter? It is alot easier to keep stocked with 5W-30 (I buy by the case) than to have to stock both weights. (I asked a guy at Pep Boys to "split a case" between weights and he near about came over the counter at me!)
Of course, since I live in New England, the term "warm weather" is relative , to say the least. I just changed-out my oil to 5W-30 now that "the frost is on the pumpkin". Could I safely get away with running 5w-30 in Spring, Fall, and Mud Season as well as in Winter? It is alot easier to keep stocked with 5W-30 (I buy by the case) than to have to stock both weights. (I asked a guy at Pep Boys to "split a case" between weights and he near about came over the counter at me!)