Cold weather oil performance

[ledslinger]

I entered some oils on the Widman visc calc and saw some surprising results.

GC and OW40 Lubro Moly are both thicker than 5W20 conventional (Mobil Super) even at very cold temps.

GC is thicker than conventional 5w30 Mobil Super, and 0W40 LM is only slightly thinner.

cSt @ -20 C

0W20 PP 1477
5W20 Mobil Super 2218
GC 3047
LM 0W40 2876
5W30 Mobil Super 3024

 

[bepperb]

Yes. The increased viscosity index of synthetics generally isn't enough to overcome an oil that is of a lighter grade... at least until you get down to the pour point.

GC is a pretty thick 30 weight, it's thicker than most 5-30 and 10-30 oils.

 

[JAG]

I'm not sure at what cold temperature the predictions become too inaccurate but -20 F might be too cold. Does anyone know? It certainly doesn't take into account high shear rate effects on viscosity which is very relevant in a running engine.

 

[cp3]

I think that is about the max that most say is fairly accurate. It is also said that it is beyond this point that the 0wXX oils show a bigger benefit.

 

[A_Harman]

Don't trust the viscosity calculator much below 20C, although some here say down to 0C.

 

[ledslinger]

Originally Posted By: A_Harman
Don't trust the viscosity calculator much below 20C, although some here say down to 0C.


I suppose it can't be correct if it considers all base stocks to behave the same at varying temps.