What Castrol Oil?

[Idaho Red Rocket 3]

Here is a little tale about change the filter and top off. I lived in NE Baltimore city as a kid in the 60's. Not far from my house were 2 C&P Telephone Co. service offices. My Dad had a friend with a used car lot and repair shop across the street from one of them. Dad's friend would often do work on the phone company trucks. He told us one day that the phone company only changed oil filters and topped off. Never changed the oil completely. They believed at the time it was adequate for the service life of their trucks which was over 100K mikes. Now keep in mind that was back in the 60's with "good" old dino oil. I think we were mostly using straight 30 weight or 10W-30 at best back then.

They also were testing the center brake light theory back then. Now it is standard on every car. Who can say ? Maybe there is some validity to change and top off. It would be interesting to see some in depth scientific details about the subject. For now, I will continue to change both and do so way more often then Porsche says to.