I've got a '97 Ford I bought new in Feb. '98. This is technically a 24 year old car with 41K miles. I do 5K mile OCI's on conventional oil (Exxon Superflo) regardless of elapsed time. Hasn't seemed to have any negative effects on it. The oil I'm using in it is oil I had in my garage when I bought the car new. What's the difference in it sitting in the oil pan or in plastic bottles on a shelf in the garage? Years ago on an old oil burner/leaker I had I started pouring oil from my other cars in it as topping off oil. When I sold the car it had been 31K miles without an oil change. There was no knocking in the engine and the guy that bought it drove it another year or two after buying it from me and only scrapped it because it wouldn't pass emissions testing.