oil expert...what mean W in 20W50

[Zef]

Saw a lot of different info on that...Aeroshell state that W mean ashless dispersant...I saw on another website that it mean winter, so the oil can be used on winter time...Any more info on that W...I'am just curious...Thanks...Syl

[ljowdy]

It means Weight

[emac]

ljowdy

Bingo !!

[morrisjm1]

Actual it does mean "winter".

[ljowdy]

I stand corrected and in all acutality, I knew this and over the years I forgot its true meaning:

In 10W/40 motor oil, the W stands for weight, right? Wrong. It stands for Winter.

A vehicle's oil has to be thick, but not too thick. It is important that in the winter, the oil be thin enough to allow for the engine to start. But when the engine is warm, the oil must be thick enough to lubricate properly. That's where the numbers come into play.

Neither number corresponds to an actual 'weight,' even though that is the term most people use when referring to motor oil. The viscosity (flow resistance) is tested by allowing a small amount of oil to flow through an aperture. The quicker the oil flows, the lower the rating numbers.

The first number rates the viscosity of the oil at a temperature of 0 degrees F, mimicking cold winter weather, which is why the 'W' designation is added at the end of the first number. The second number repeats the test at 210 degrees F., or normal operating temperature for a fully-warmed engine.

The 'W' rating can be 5, 10, 15 or {20;} lower numbers mean the oil is thinner in cold temperatures, necessary for icy climates. The second number rating (meant to represent normal operating temperature of an engine) can be 20, 30, 40 or 50. Warm-weather spots usually require oil in the upper end of that range that can handle extreme heat.

[BK911]

I always wondered how oil gets thicker as is heats up.

[Porsche_monkey]

I believe its counterintuitive, i.e. it flows like a straight 50 weight when warm, it flows like a 20 weight when it's cold.

[cashflyer]

Long chain polymers.

[morrisjm1]

If I remember right, which I rarely do these days, a 20w50 would flow like a straight 20 weight up to the temperature at which a straight 50 weight would flow like a straight 20 weight. Basically, it doesn't actually get "thicker", it maintains the smaller number viscosity over a wider temperature range than a straight weight oil.

We're reaching back nearly 30 years in the old memory banks, so I could be wrong.

Mike

[IROC]

I may be saying the same thing that has already been said, but W does mean "Winter". It simply means the oil is rated for use in winter.

As for the numbers, in a 20W50 oil, for instance, I always understood it to mean that the base stock of the oil is a 20 weight oil, but that it had viscosity improvers added so that it will not thin out any more than a straight 50 weight oil would at temperature (180F or whatever it is tested at). In other words it behaves like a 20 weight oil at cold temps and won't thin out any more than a straight 50 weight would at high temps.

[Zef]

From Aeroshell FAQ website...:

Does the W in AeroShell Oil W stand for winter?

No. The W is just a model designator to differentiate between AeroShell ashless dispersant oils (Oil W) and straight mineral AeroShell oils which have no letter designator.

[ossiblue]

Originally posted by Zef
From Aeroshell FAQ website...:

Does the W in AeroShell Oil W stand for winter?

No. The W is just a model designator to differentiate between AeroShell ashless dispersant oils (Oil W) and straight mineral AeroShell oils which have no letter designator.

Just to clarify, if you read the Aeroshell information, they use the "W" twice in an oil's designation--once to identify it as ashless dispersant, and again in the commonly used form for winter. Thus you will see something like, "Aeroshell Oil W 15W-50" (Forgive me if this particular fomulation doesn't exist, it's just an example to show how confusion and many barroom bets can get started.)

[Zef]

So if everybody is OK with that...That famous W mean winter...

[cygtoad]

Originally posted by IROC
I may be saying the same thing that has already been said, but W does mean "Winter". It simply means the oil is rated for use in winter.

As for the numbers, in a 20W50 oil, for instance, I always understood it to mean that the base stock of the oil is a 20 weight oil, but that it had viscosity improvers added so that it will not thin out any more than a straight 50 weight oil would at temperature (180F or whatever it is tested at). In other words it behaves like a 20 weight oil at cold temps and won't thin out any more than a straight 50 weight would at high temps.

+1