What oil weight

[BXMMCC]

A quart of oil - 32 ounces - is a fluid measure - volume. A pound - 16 ounces - weight.

A quart of water weighs about two pounds.
Gasoline weighs about a pound and a half per quart.
Lube oil is somewhere in between.

Fluid ounces have nothing to do with weight.

 

[slowrev]

Correct you are fluid ounces have nothing to do with weight. So why is the viscosity of oil referred to as weight ? Just curious, anyone know ?

 

[RalphVa]

A quart of oil is short of 2 pounds, because it is lower than the specific gravity of water.

Don't know why oil viscosity is called a "weight". I would have called it "wait". In the winter, in can be a long wait for a higher viscosity oil to flow. Some won't flow at all.

Ralph

 

[BXMMCC]

More stuff than everyone doesn't need to know (from a Web page googled oil weight):

The way oil viscosity is measured is with a Saybolt orifice viscometer, which is basically a cup surrounded by a water bath which keeps the temperature of the oil sample constant. There is a plugged opening in the bottom of the cup, which is opened when the oil is at the proper temperature. The oil is captured in a 60ml flask and the amount of time required to fill the flask is recorded.

A SAE30 oil takes 58-70 seconds to fill the flask at 210F,
an SAE40 oil takes 70-85 seconds, and
an SAE50 oil takes 85-110 seconds.


There is also a test for low-temperature viscosity that is designated by a "W" suffix on the SAE viscosity rating.
A SAE5W oil takes less than 6000 seconds to fill the flask at 0F.
An SAE10W oil takes 6000-12000 seconds, and
an SAE20W takes 12000-48000 seconds.

I'd assume that the winter oil testing leaves the test engineers with plenty of time to relax while waiting for the test to conclude! Ah, the life of a petroleum engineer!

A "multiviscosity" oil is simply an oil that has been rated using both tests. Nothing magic about it, except that sometimes the composition of the oil has been tweaked to flatten the viscosity-temperature curve.

Note that a SAE30 oil and a SAE30W oil are not the same thing, as they are measured using different tests.

 

[BXMMCC]

And for those who really are curious:

Oil weight

 

[Larry_T]

BXMMCC very interesting Larry thanks

 

[slowrev]

All of the oil viscosity tests seem to deal with temp/volume/time. Where does the weight come in? Might have missed something though.

 

[BXMMCC]

From the howstuffworks webpage:
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.

 

[slowrev]

Thanks for the expanation on the "weight" thing. I sort of assumed that from scanning the article, but you know about assumptions /forums/images/graemlins/smile.gif

 

[GerardC]

</font><font color="blue" class="small">( And for those who really are curious:

Oil weight )</font>

Very interesting. Thanks for the link.