Synthetic oil and piston ring?

All I know is I switched to synthetic on my 10 year old Toyota Solara and...the oil never got black between oil changes even if I went a year or 12,000 miles ( I usually change it ever 6 months tho)...I also noticed the car seemed to run smoother and quieter...and it never ate a drop of oil between changes..and I also noticed that my gas mileage improved by about 2 miles per gallon. I love it, and will use it in all my cars. Also it does not void a new cars warranty..that should tell you that even the auto makers approve of it. good luck.