I usually don't start threads-but I have a delema. I recently put the 10W-30 blend in my Sentra here in Pa (even though winter is coming). We do get normally a vew days at zero and can get as low as -15F. I can live with the fact that I used the 10W but since I understand the 5W blend has more Group III. I wonder if I should go with it (5W) in the future??