Quote:

Quote:


Real eye opener if this guy is on the mark? Kinda tosses most diesel oil out the window. Cost per quart looks like Mobil 1 5W-30 Full Synthetic is the winner.



Scar test is just one of several indicators of actual in use performance to consider. Probably a more important test for greases than motor oil. Although I tip my hat to him for going through the trouble to do this test, there are questions about the control of his procedures, test environment and equipment. That doesn't mean they are or are not valid results, just we can't be sure.

"Choosing engine oil for Corvairs" by Widman is probably the most readable overview of motor characteristics. It covers viscosity, pour point, differences in base stocks, and a bit on additive packages. Read that and you'll have a much more complete view of motor oil performance.
Illustrated Pdf in English from his hobby pages http://www.widman.biz/Corvair/English/Links/Links.html or his business pages http://www.widman.biz/English/Selection/oil.html

Also on his websites are some other good papers on gear oils and case studies of failures he's had to deal with.



Good info thanks. I'm mostly interested in flat tappet cam lobe protection. I figure if it can protect the cam lobe, the crank/rod/cam bearing wear will be low as well.

So now I'm thinking I want the highest HTHS (ASTM D4683) combined with the lowest viscosity.

What is the difference between the "viscosity index" and the viscosity ratings at 40C and 100C or more importantly, which rating/measurement is most important to look for in motor oil? I'm thinking the 100C measurement.