My friends son has a 99 corolla with 290,000 miles that sometimes had a slight piston slap. I heard it tonight and it sounded pretty quiet he used pennzoil 5w30 syn blend.. I always found that syn makes engines with piston slap louder...I was impressed... Does anyone have a used oil analysis on that oil it seems to be pretty good in his abused corolla.. Is that oil the same as the yellow bottle mixed with synthetic?