Brad Penn 10-30 vs 20-50, Weight vs Temperature Options

[1988Hawk]

On a 88 degree day in Chicago I have tested two oil weights and have gotten the following results:

1. Brad Penn 10-30W, with peak running temp 205 degrees.
2. Brad Penn 20-50W, with peak running temp 225 degrees.

Both exhibited acceptable pressure, so the question is which one would you select for summer driving???

[Jake Raby]

Viscosity can also affect the type of flow through an oil cooler, possibly forming a boundary layer at a higher viscosity that insulates the hot oil further from the internal surface of the cooler.

Exactly. I have carried out years worth of development for and with Joe Gibbs Driven Racing Oils to study these effects with different base oils and additive packages in European engines. This is limited to Porsche, but also includes MB and BMW, and even SMART engines.

Thick oil often builds more heat, unless the internal clearances of the engine favor it, and unless the characteristics of the oil allows it to not only collect, but also shed heat.

At this level we use cinestoke as the unit of measurement, and its well beyond what an oil is rated at only at 212F, as directed by the API.

My record is 360 chassis dyno pulls in a week, and 13 test oils. The ONLY goal with those tests was to gather trend data to support the changes the engine saw in regard to oil and engine temperature with the different oils.

No general statements can be made, the variables from oil to oil and etc are too great. I am most concerned with HTHS data and the oil's ability to maintain pressure at idle, when at elevated temperatures. This is NOT to be confused with viscosity, as viscosity index comes into play at temperatures well above the API 212F test.

[scott_in_nh]

At this level we use cinestoke as the unit of measurement, and its well beyond what an oil is rated at only at 212F, as directed by the API.

We use Centistoke to measure viscosity as well. For the nerdy among us who would like to know (but don't already) there are two types of viscosity:

Dynamic viscosity - measured in centipoise [cP]
dynamic viscosity measures to force required to shear the fluid

Kinematic viscosity – measured in Centistokes [cSt]
Kinematic viscosity is the dynamic viscosity divided by density

So in other words if you have the same volume of two liquids that have the same "thickness" but one of them weights more, then it will have the same Dynamic viscosity but a higher Kinematic viscosity.

The higher Kinematic density (Centistokes) means that it is harder to pump.

EDIT: my mistake, I thought jake made a typo, cinestoke is also a unit of measurement for viscosity = unit millimeters squared per second.
I am not familiar with this one, maybe Jake can fill us in.