My 2 cents is that oil makers are wanting to cover every field they can, since cars are lasting longer than from the 70's/early 80's there marketing High Mileage, Heavy use, Higher RPM's, SUV, Light Truck, Heavy Truck etc... Is there much or any difference I don't know...But as we all know the oil companies can do and say anything they want with minimal regulations from the government... I'm at 152k miles and have used Mobil1 for the last 70k and I don't see myself ever changing brands/types. 5w-30 Winter and 15w-50 in the summer. They do make a High Mileage 10w-30 and 10w-40

http://www.mobiloil.com/USA-English/...s/Mobil_1.aspx