Join Date: Jul 2008
Location: Railton, Tasmania, Australia
Re: Oil Thread - SAE ratings
The lower number is the oil's cold viscosity behaviour, basically an indication of its pumpability when cold, among other properties. W stands for winter. The higher number is the viscosity number which represents the oils behaviour at high temperature, the standard being 220 degrees F (from memory). Synthetics are basically able to be engineered to have a wider temperature/performance range than mineral products, this is partly because of the molecules being more uniform in size, and many other complex reasons. If you are really interested in understanding this I suggest you google it, there's heaps written about it, just wade through the info and take in what's of interest to you.
1987 Yamaha TY250R
1991 Aprilia Climber 280
1988 K100RT (the pack horse)
2005 K1200LTE Light yellow metallic