Originally posted by IS2Scooby
Then it's ON!

It used to be that oils only came in a single viscosity, such as SAE 40, SAE 30, SAE 20/20W, &; SAE 10W. The larger the number the heavier the viscosity, or to say it another way, the oil is thicker as the numbers go up. Generally, the lower numbers are for cold weather use, and vice versa. Now they are combined in multiviscosity oils, like 20W50, 10W40, 10W30, and 5W30, meaning the oil will serve over a wider temperature range. Where you once changed to "winter grade" oil in the fall and back to "summer grade" in the spring, you can now use the same oil at any time of the year. Most manufacturers are now recommending 5W30 oil for year round use, even in fairly heavy duty applications. The idea is that it flows more readily under both hot and cold conditions, providing initial lubrication earlier when a cold engine is first started, and carrying away heat more efficiently when the engine is hot. It also creates less friction or drag on internal engine parts, allowing better fuel economy and slightly more power output, too.