The Stovebolt Site Forums The Shop Area Engine Shop All Straight Weight Oils have Winter (W) Viscosities, Right?

All straight weight oils, such as SAE 30, have "Winter" weight viscosities ("W") but it's just not reported on the bottle, right? If you ran a "cold test" on your SAE 30 oil, you might have a 20W30 or 10W30. It's an xW30 where x = unknown.

Has anyone seen where the winter weight number has been reported for a straight weight oil? Just curious.

To figure that out, you'll have to look up look at the SAE J300 classification. The lower the number, the better the flow at low temperatures.

There are charts on the web that show the J300 viscosities of straight weight oils in cold temps.

Here is the information you need all in one place:

https://en.wikipedia.org/wiki/SAE_J300

I don't want to figure something out. I wonder if anyone bought some Pennzoil SAE 30 and did the cold test on it (the special equipment would be required) and reported the winter weight. The number isn't on the bottle but it does exist. The winter weight probably varies between different batches.

No it's not on the bottle but the chart shows its viscosity properties in cold weather.

The number SAE30 designates it's properties at engine operating temperature. All SAE30 oils must meet the same standard , regardless of brand.

This may help you. But as you can see, it's THICK.
A multi-viscosity oil such as 10W30 has a viscosity of 30 weight at 100C and a viscosity of 10 weight at 0C.

If it's straight 30 weight, I don't think you'll find a "W" rating; as 30 shouldn't be used in winter nor would it pass the minimum viscosity tests for 0 deg.

I'm having trouble explaining myself.

A straight weight oil, such as SAE 30, is actually "xW-30" where x is not known to the consumer. Perhaps it varies from batch to batch. Perhaps the x is too large. There has to be a result of some sort when you test the oil in a "cold test" machine. What would be typical?

Have you ever heard of someone putting a straight weight oil in the "cold test" machine and determining its winter weight number?

I'm just curious about a typical result. 25W30? or ?

If you did a cold test on straight 30 weight oil, it would come up as 30 weight. Like the chart I posted, it would have a dynamic viscosity of 1.53+/- N s/m^2 versus a dynamic viscosity of 0.01 N s/m^2 at 100C.

The only thing that would change that would be adding viscosity index improver to the oil, which would then make it NOT straight 30 weight.

In other words, straight 30 weight oil is ------ wait for it -------- straight 30 weight oil.

The '52 Chevrolet operators manual suggests that if you will be operating in an extreme cold environment, you need to add kerosene to the straight 30 oil in order to be able to turn the engine over to start it.
So, with that said, in 1952 the straight 30 weight oil was in all likelihood straight 30 weight.
I do not understand why oil manufacturers today would formulate 30 weight any differently today than they did in 1952.
If they did add something to make today's 30 weight multi-viscosity, would that not be considered deceptive to the consumer?

It wouldn't be straight 30 weight then. If there were something added to a straight 30 weight (called viscosity index improvers) it has to be designated on the the label and would be considered a multi-viscosity oil, not a straight weight oil.

By definition, to meet SAE standards, 30 weight oil must meet all tests for 30 weight oils but MUST FAIL tests for 20 weight oils, for example.

You should also be aware that the numbering system 10w, 20w, 30, 40, etc. bears no relation to any specific test. The numbers merely rank oils in order of low viscosity to high viscosity without regard to any actual measurement. That is, 40 weight is not twice as viscous as 20 weight. The numbers simply make it easy for consumers to figure out what oil is thicker and what oil to put in their cars.

Well, since we seldom get much real winter weather here (aside from a freak cold/ice storm every once in a while) I just use 30 weight all the time.

30W oil is 30W30.
20W oil is 20W20.

If it is a straight weight weight, it is the viscosity of that weight oil at all temperatures.

Just to be clear, it is not the *same* viscosity at all temperatures, it is the viscosity of that weight oil.

Woodsy Owl says "WHOOOOOO- - - - - -CARES?" 30 weight oil is too thick for anything but extremely hot climates. You'll beat the rod bearings to death on a cold startup before they get enough oil pressure to lubricate them properly in all but the hottest summer weather. On an old engine with three times the recommended rod bearing clearance due to worn bearings, it might prolong the engine life a while before it beats itself into oblivion.
Jerry