I used Brad Penn in the 408 for the first year, but it would use a half quart between changes, switched to VR-1, all is good
Brad Penn always seems a lot thicker than what the viscosity is showing on the label, and seems "stringy" when you pour it in, compared to my other brands
That's good to know. I also find that BP 5W-30 and 0W-30 requires topping off between oil changes (about 2000 - 2500 miles).
Relative evaporation between oils can compared using the volatility test results. Sometimes the NOACK volatility for can be found on spec sheets and almost always the Flash Point. The flash point is obviously a less direct correlation to the evaporation rate but its better than nothing. Volatility can vary between grades as well as between brands.
The actual thickness (viscosity) of any oil can be usually found on the manufacture's spec sheet. Richard Widman has an on-line calculator that can be used to show the viscosity at any temperature given viscosity at the two standard temperatures on those sheets.
Graph & Table for up to 4 Oils Actual oil viscosity definately varies with the allowable limits of the grade.