What is it made of?

As Larry said, quality premium oils are better than what was available when the car was built, will suit the engine fine. If you want to further extend the life of your engine, a quality synthetic oil will help, which have high-pressure lubes for high-shear such as MoS2 to replace the zinc in the old formulations, more expensive additives but better than zinc.

Some additives can be good for your car/engine, but if you don't understand the additives and chemistry involved, there is more opportunity for damage than for improvement (ex: Slick50).

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Gone to the dark side

- Jeff