It depends where you live....here in Cyprus we use 15W50 in Summer for most petrol cars, or even 20W50 because it gets really hot...in winter people go with 15W 40 or 10W30. It also depends where you live...i had my oil change in Sept and i use 15W50. Honda Authorize Repair Center told me my 0W 40 mobil one was too thin, so did my mechanic that did return my Mobil 1 0 W 40 and got me some 15W50..I think lower number will warm up the car faster in winter and are better for cold starts, better fuel economy when is cold.