# xWx explanation

```>
>Could someone explain to me the xWx "oil grade description".  I know one of
>the x's is a measure of the viscosity (right?)?  For example, 15w50?
>
>Thanks!
>
>       -- Mark.
>
>===============================================================================
>Mark Salem				URSA Group, Dept. of Computer Science
>msalem@cs.utah.edu			University of Utah
>===============================================================================

below is a parts of a posting from the network news that ran
through the quattro listing a month ago:

More Than You Ever Wanted to Know About Motor Oil
By Ed Hackett <edh@maxey.unr.edu>

The weights given on oils are arbitrary numbers assigned by the S.A.E.
(Society of Automotive Engineers). These numbers correspond to "real"
viscosity, as measured by several accepted techniques. These measurements
are taken at specific temperatures. Oils that fall into a certain range
are designated 5, 10, 20, 30, 40, 50 by the S.A.E. The W means the oil
meets specifications for viscosity at 0 F and is therefore suitable for
Winter use.
The following chart shows the relationship of "real" viscosity to their
S.A.E. assigned numbers. The relationship of gear oils to engine oils is
also shown.

_______________________________________________________________
|                                                             |
|      SAE Gear Viscosity Number                              |
|  ________________________________________________________   |
|  |75W |80W  |85W|    90        |        140             |   |
|  |____|_____|___|______________|________________________|   |
|                                                             |
|     SAE Crank Case Viscosity Number                         |
|  ____________________________                               |
|  |10| 20  | 30 | 40  |  50  |                               |
|  |__|_____|____|_____|______|                               |
______________________________________________________________
2  4  6  8  10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42
viscosity cSt @ 100 degrees C

Another way of
looking at multi-vis oils is to think of a 20W-50 as a 20 weight oil that
will not thin more than a 50 weight would when hot.

Dan

```