Thank you very much for that very useful information. I did not know that the 2-piece oil ring was a racing design. That makes sense. I suppose Toyota was trying to meet ambitious mpg mandates and so used a design that the engineers must have known would clog. Care Care Nut on youtube states that the 2AR-FE avoids the problem by using thin 0W oil and a built in oil separator (catch can). The 2AR pistons look the same as the so-called defective 2AZ pistons.
Mahle/Elko-konig are big users for racing application pistons for a typical single compression ring piston, Thin oils may aide. I like the ring design , cause as long as it doesnt completely clog up, oil usage is like zero, and this is even with like 20w50 oils, but again Im talking 15 hour or sub 1000 hour oil changes is my experience, before 30 or 40,000 mile tear down and replacement.
I dont know if a very thin Group 4 type oil would prolong carbon build up in the oil ring ports, but to me street cars, the typical 3 peice ring with larger oil return holes , seems better for longevity to avoid the carbon build up issue (pluggage).
My wife has a 2003 Rav 4 190,000 miles , I add maybe half a quart in 4000 miles, Id say it has a traditional 3 peice oil ring, but I dont know for sure. But I was Surprised, when I saw what oil ring toyota was using for vehicles showing long term oil control issues, that you normally want to see go 200,000 miles without oil usage.
