I actually use the Fram PH5 and Castrol 20W-50 synthetic blend.  A friend with a 1978 just lost the cam on his 350 and was told that it was due to a lack of zinc in the motor oil.  Is this true and should I be putting an additive in my oil?  The engine is about to turn 60,000 original miles. I use about a quart every 500 miles (I know I'm avoiding a rebuild) and so I am always in a refill process.  Any thoughts my fellow C-3 ers?

It's always interesting when someone loses a cam they automatically assume it's caused by the oil.  I'm not claiming it's not the case here but my own belief is it's become a convenient excuse by those with an extremely high mileage engine, abused engine or improperly maintained engine.

        I have used Fram Filters and Castrol GTX 5-30 in all  domestic vehicles for years and never had a problem. But I use K/N filters on my 77 and 05, with Castrol Edge synthetic 5-30. I think your oil is the most important part and Castrol is one of the best.

From personal experience I wouldn't use synthetic oil in these old cars..main reason being oil leaks..even the new engines that are essentially glued together will leak more often than not when used..I do use Brad Penn oil though..10-40..the real reason to use synthetic oil is on cars that are driven alot of miles in a short period of time..then it's worth the extra lube life..other than that it's a waste of money.

I have just replaced 5 out of the 8 valve seals on the right side of my ZZ4 crate. When I had that engine dropped in, I was told to use 'break-in' oil for the first 1,000 miles, then a blend of break-in and Mobil 1 for another 1,000 and then go to Mobil 1.  This new mechanic I found told me that the valves on the right side were never hot lashed, I had a loose push rod, and a loose rocker arm.  All those issues combined to the fact that I did not have enough oil in that valve train, which is what contributed to the compromised valve seals.  He told me that a synthetic oil will indeed find the tiniest little place to leak.  So I am switching to Castrol GTX 20W-50.  I agree that the viscosity may seem a bit much, but I live in SC and we all know about how much heat these engine compartments build up. 

For some time now I've wondered about the whole synthetic thing - is it really worth it?  I'd be more than happy to go back to conventional, but I do believe there is some truth in the zinc/ZDDP issue.  It sure seems like it's a needed ingredient for a flat tappet cam motor.  I guess you could just get any oil and then add an additive, but I'd rather use an oil that has everything needed included.  Are there any good conventional oils with ZDDP already included?  

Doesn't the Shell Rotella for diesels still have the zinc, etc in it?

The reason they reduced the amount in oil is the detrimental effect it has on cats.

I don't think Rotella has the 1200 ppm level anymore.  I thought I read somewhere that 40w oil and over does have the higher levels of zinc.  Bobistheoilguy.com is usually a good place for info on this.

There's a great article re: Oil in the Jan 2012 issue of Corvette Magazine.