Thanks a lot_you said 50 is thinner than 60 I mean by 50 or 60 is 5w50 and 10w60
September, 14, 2012 AT 6:57 AM
Those are both "multi-viscosity" oils. It's been so long since I had to think about this that I've forgotten the physics, but it doesn't mean the oil changes its viscosity at different temperatures. (Viscosity is measured at a specific standardized temperature). It means it will act like a certain oil when it gets really cold. A straight-weight oil will get much thicker when it's cold. A multi-weight oil will thicken less as it gets colder. That helps it flow better when starting a cold engine. It will also thin less when the engine is hot. That helps it maintain its lubricating properties. To do you a better job than that at explaining it I'd have to dig out a textbook.
Both of those oils seem awfully high for newer engines. 10W-40 used to be the most common for summer use. Some manufacturers went to 10W-30 back in the '80s and '90s. The thinner oil pumped easier so the oil pump theoretically put less load on the engine. Many engines today call for 5W-20 or 5W-30. To me that seems like water but the thinking is the oil flows easier, the engine doesn't work as hard to pump it, and fuel mileage should improve. Hmm.