Every (and I mean
every) early engine failure I have ever been made aware of or have personally worked on as a master tech and engine builder has employed API grade synthetic oil. CAUTION this experience or coincidence is not statistic relevant
One of these was an 80's vintage Toyota Camry with a galled oil pump plate at 147K miles. Well at least it was an easy fix. Others were multiple cadillac northstar and 4100 and 4500 failures - but lets not go THERE. Another anecdote into evidence is my cubicle-mates 82 v6 ranger with 366K miles all on valvoline 10-30 with oil changed every 3-5K miles and all engine performance issues addressed in a timely manner. No Oil burnt here. Oh yeah they dumped a ton of Zinc phosphates in the oil back then! How can his catalyst still be working??? Oh he just informs it might be time for renew timing chain for #1st time.