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For the "older" cars I like to use Valvoline's VR1 series with high zinc content for bearings. (Using 10w30 now in my 72'C3).
As for cleaners, Techron is great stuff on a full tank just before an oil change. (or just run Chevrons fuel for a few tanks and that works fine also)
Marvel Mystery Oil (that someone mentioned) is excellent if you are suspect at all that your engine has oil crud inside. Run it as one of your quarts for an oil change (with a 10w30) and for 15mins. Will clean your lifters and is safe.
I was more thinking about fuel additives that clean your carb/injector
My wife's Volvo occasionally needs a fuel system additive to clean the injectors. My experience has been that Valvoline Complete Fuel System cleaner works better than the others.
Marvel Mystery Oil is actually a great product. Have seen it break free many frozen/sludged lifters as well as PCV valves. Honestly for what they claim its pretty good stuff
Designer Imagines A Corvette That Looks More Like a Corvette Than the Corvette
Slideshow: A Jaguar designer's personal project imagines what a modern front-engined Corvette might look like if Chevrolet revisited the golden age of the Stingray.