Widman viscosity graph

Captain Howdy · Mar 2, 2009

http://www.widman.biz/Seleccion/Viscosidad/Conversiones/Graph/graph.html

I plugged the numbers in for my last oil fill, RP 0w-10, and it shows the RP to be a very thick oil at lower temps. Even thicker than the conventional oil I listed or even Mobil1 0w-40. the numbers really surpised me since we had some very colds temps this winter, several -5 F and below days.

Anyone know why this would be?

Thanks
Mark

d00df00d · Mar 2, 2009

It must have a relatively low viscosity index. That would means it would thicken relatively quickly as the temperature drops.

Kernel Potter · Mar 2, 2009

Looking at how much thicker than the others RP0w-10 is at cold temperatures but is still 6.8cst at 100 celcius, My guess is it has a really low viscosity index. In fact it looks so newtonian, relatively speaking, that it almosts seems like it would be made with group I oil and a less than adequate additive package. I really doubt it actually is but the numbers don't seem to add up.

Kernel Potter · Mar 2, 2009

Beat me to it d00df00d

Bryanccfshr · Mar 2, 2009

I agree, Very low Viscosity index. You ought to run the minimum temperature to -35Celsius . 0 is simply the freezing point.

XS650 · Mar 2, 2009

Originally Posted By: Bryanccfshr
I agree, Very low Viscosity index. You ought to run the minimum temperature to -35Celsius . 0 is simply the freezing point.

He's using data points from 40C and 100C. Extrapolating to -35C would me meaningless. I think 0C is a bit of a stretch.

CharlieJ · Mar 2, 2009

This application. I like it.

mechtech2 · Mar 2, 2009

Who would have guessed that anybody's 0-10 would have such poor cold flow!
I should have been a shoe in for the best.
I am really surprised.

d00df00d · Mar 2, 2009

Well, as a caveat, XS650's objection is valid and important: you can't just take two kinematic viscosity measurements and extrapolate a whole graph from them. There's a whole lot more to it than that.

However, it wouldn't be surprising to see lackluster cold flow from a 0w-10. Don't let the thinness fool you: 0w-10 is a tiny viscosity spread. It's still a fair bet that that oil has a low viscosity index.

Too bad Royal Purple won't release the specs on that oil...

FrankN4 · Mar 2, 2009

When you consider that the 0W-10 has a VI of 95 and the 0W-20 PP has a VI of 170, you can make sense of such a wide spread.

Audi Junkie · Mar 2, 2009

PP 0w-20 is amazing.

Captain Howdy · Mar 3, 2009

Originally Posted By: FrankN4
When you consider that the 0W-10 has a VI of 95 and the 0W-20 PP has a VI of 170, you can make sense of such a wide spread.

How'd you come by the number 95 VI for RP 0w-10?

d00df00d · Mar 3, 2009

I'd like to know as well. Royal Purple's page for XPR says they don't release specs on those oils.

oilyriser · Mar 3, 2009

This is like extrapolating a stock market graph.

FrankN4 · Mar 3, 2009

Viscosity Index is an empirical number, that is it can be disproved or verified by experiment. It indicates the rate of change in viscosity of an oil within a given temperature range. If you set the temperature from 40C to 100C, the VI is a mathematical index that is repeatable, not a guess or estimation. You can then either "do the math" or plug the parameters into a pre programmed calculation program. That is what I did.

When I first started to check the true mathematical VI against the advertised VI of the oil brands, I noticed they sometimes matched perfectly and were sometimes off 3 or 4 points. I talked to a chemical engineer(yeah, not a tribologist) of one of the better known oil companies. He said the advertised/published information was averaged. If the 100C cSt was listed at, just for example, 10.5, the various batches might be 10.25 to 10.75, and so with other values. If I then take the published VI and compare it with the mathematical VI, there might be disagreement, but if more than 3 or 4 points, there is a greater variation in batch averages.

If you take the parameters given for the PYB, the calculated VI will be from 155 to 158, depending upon if you round off at even, 1/10, 1/100, etc. By the same process, the PP would be between 166-168.

A higher numbers indicate a low change, a lower numbers indicate a relatively large change.

Audi Junkie · Jun 15, 2009

I did not realize how awesome this tool was when I first looked at it because I did not load up the page. It's actually and old post, and I had a computer fault at the time. I've been wanting to use a good graph tool for a while, thanks a lot Widman.

Anyway, I see he has it preloaded with typical dino oils, even HDEO 15w-40. It also can be tweeked to look at a specific temp range. It seems like 100cSt is the sweet spot for start-ups. Warm 30 weight multi has this visc. When you deviate from that you start to have your "flow issues"....lol.

It's late, but soon I plan on some more posting on various oil visco-comparisons.

I still want to see M1 0w-30 and PP 5w-30 compared at 0f.

http://www.widman.biz/Seleccion/Viscosidad/Conversiones/Graph/graph.html

Captain Howdy · Jun 15, 2009

I'm still amazed by this, thus exposing my poor knowledge of oil properties. Royal Purple 0w-10 is designed for high temps, i.e., drag racing(doh!)... or summer driving.

I'm back to PP 0w-20.

zoomzoom · Jun 15, 2009

how can 5W oil be thinner at 0C then 0W?

I remember using similar calculator only to be told by the "elders" on this board that extrapolation sub 40C temperatures using viscosity index is not very accurate!?

ekpolk · Jun 15, 2009

Originally Posted By: Audi Junkie
PP 0w-20 is amazing.

And it "felt" very nice when I ran it in my Hybrid Camry. Alas, you pretty much have to special order the stuff to get your hands on any. . .

Captain Howdy · Jun 15, 2009

Originally Posted By: ekpolk
Originally Posted By: Audi Junkie
PP 0w-20 is amazing.

And it "felt" very nice when I ran it in my Hybrid Camry. Alas, you pretty much have to special order the stuff to get your hands on any. . .

...and that's what I was doing. I'll be going back to PP 5w-20 when my small stash is gone.

Widman viscosity graph

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