Oil Temp vs. Oil Weight Options

[NJ914Guy]

Can someone please set me straight on this.

Given summer time driving (70-95 degrees temps outside):

If a 914 is running 20w-50 oil vs. 10w-30 oil, I know that the 30 weight is thinner oil, but which oil would run lower oil temps?


Thanks, having a mental block moment here (IMG:style_emoticons/default/beerchug.gif)

[Joe Owensby]

There are threads discussing this before. The oil cooler bypass valve is essentially a thermostat. It allows oil to bypass the cooler when the internal pressure is above a certain pressure. It was originally designed to do this with cooler oil. If the springs on the bypass valve are not correct, then a higher viscosity oil will just pass less oil through the cooler until it heats up to a higher temperature than would be rrequired on a low viscocity oil. Doing so effectively lowers the viscosity of the oil due to the higher temperature. If you look at the viscosity charts of 30 and 50 weight oils at 200 degrees, there is a significant difference, as per design. I use the 20-50 weight oils per recommendations by the "experts", but I haven't seen any real data supporting this. I wonder why the Porsche engineers specified 30 wt. For the record, the "weight" term of the oil refers to the viscoty, not the actual weight as in the previous post.