The article was about ring placement , deposits and oxidative thickening . It speaks of the CAT 1N gas engine and further down about a different diesel engine .
Good article I suppose but was generalized because one piston used an acculumlator groove , others did not and there was no mention of piston ring tension differences between the three but the was speak of ring lift angle " on page 13 . Look at the 50wt .
Ommitance of the accumulator groove and it's function would have helped the article which seems more of a brief than anything .
If testing oil film thickness with 5w-20 testing apples for apples would be best I would think .