My friend took my ‘99 corvette in for an oil change and I had given him 2 jugs of Mobile 1 5W 30 Oil. The “mechanic” insisted on using 0W 30 oil because it was written on the oil cap. I spoke t him after the fact when he still believed the oil cap writing although I had checked the manual, with several corvette owners on Corvette Forum and it was not my first rodeo having had the oil changed several times before. Apparently, my grandson had replaced the original oil cap with the shiny new one.
