Viscosity Calculators don't work well below zero..

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Has been stated on BITOG a number of times, and only last couple of days has it really cemented itself to me.

Two base-stocks, same KV100, same VI (so therefore same KV40)...the two determinants on a Product Data Sheet (or MSDS for some)...two data points and the slope of a line between them.

And very very different behaviours below freezing temperatures.

brookfield.jpg


Scaling off the pic, the GrIII looks to be 60,000cp at -35C which is the limit for 5W...5C to the left (-40C), 60,000cp is the limit for 0W.

Plug the KV40 and 100 into the widman site, and you get
VI144chart.jpg


for both...clearly not what's really happening.

(Note different units, poise and stokes)
 
Now that's very interesting.

So apparently basestocks do matter,at temps common here for 6 months of the year. An oil with more pao will pump more easily in temps below freezing.
Thanks Shannow
 
Originally Posted By: Clevy
Now that's very interesting.

So apparently basestocks do matter,at temps common here for 6 months of the year. An oil with more pao will pump more easily in temps below freezing.
Thanks Shannow


Which is why CCS and MRV are relevant specs to look at for cold temperature operation (and why M1 AFE 0w-20 is probably the ultimate OTS xW-20 weight for extreme cold).
 
Exhaustive tests by GM published years ago in the SAE journal showed that their engines generally stopped starting when the CCS exceeded 30,000, generally popping and snapping acting like they wanted to start (sound familiar) but unable to overcome viscous drag.

Their results nicely matched the oil viscosities...

30 weight, starts down to +5f
20 weight down to -15
10 weight down to - 30

They also made note that 10W30 (dinosaur oil) would be some thicker than the straight 10 used for the tests.

Extrapolating, likely the 0W synthetics are good well past -40f. I have personally experienced -43 to - 47 f on several northern and mountain adventures and can verify some easy -40 starts (With 0W20).....the only one to start at a large ski lodge in Jackson Hole, Wyoming, for example.

I have previously posted some of those arctic like experiences! Dang, and the cold record for that area is -63 f at Moran Junction, just north of town and -68 at Hoback Junction just south of town. Yes this is straight temperature, not chill factor.

Ski Jackson!!

Interestingly, the GM tests showed that cranking speed was almost unrelated to ability to start. If the oil was much thinner than 30,000 CCS, when they popped they started, even at cranking speeds as slow as 6 rpm!!

Maybe why my first car, a 1941 Plymouth could start in winter with an impossibly slow cranking 6 volt system and a VERY old battery.
 
My real life experience dove tails with fsskier. 20w50 won't turn fast enough to start below 10F. 10W40 is good to -14F at least. 10W30 is good to at least -25F
 
Yes, especially with dino, the growth of wax crystals really effects the viscosity at low temperatures. The oil guru at Eaton Corp. once told me that she didn't trust the VI calculators for conventional oil below 20C.
 
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