Zinc is used as a lubricant and to help keep your oil basic (pH). There are plenty of other lubricants (better), and other pH buffers, zinc is old-school but works fine.

Lots of good syn oil out there. The plusses are: lower friction for better fuel mileage and less engine wear; faster pump-up when starting cold for less engine wear; lower viscosity at super-cold temperatures (not your problem in CA) for easier cranking; cleans engine out for better lifter operation and less gunk build-up; and extended-drain intervals for less environmental impact if your engine is running properly.

Minus is mostly cost. The "it will leak if you change a high-mileage engine to syn-oil" myth is from the '70s when it did different things with seal swell than dino oils and wasn't compatible with dino oils, and the fact that it will clean gunk and exploit existing leaks better. Mercedes' official stance some years ago (technical seminar published in The Star) was if it leaks on syn-oil, change it back or try a part-syn like Castrol Syntec et al. It will go back to its old self.

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Gone to the dark side

- Jeff