New "SM" API Motor Oil

I’ve been reading a lot of information lately on the new API motor oil “SM” rating. It appears the Zinc content is now almost non-existent in this oil in an attempt to prolong the life of catalytic converters. I’ve read that Zinc is necessary to protect flat-tappet lifters. I own a 2000 Isuzu Amigo 3.2L DOHC, a 1982 Cadillac 6.0 L 4bbl, and a 1965 Corvette with 327 ci., all with stock valve trains.

Do I need to worry about this Zinc issue in any of my vehicles? I do notice that there are zinc oil additives available, one of them a GM Product.

Check out and you should find the pros and cons of SM oils and the zinc issue. I sleep well not worrying about it, personally.

Like jayhawk says check out, but more specifically look at the virgin oil analysis page: Here you can see what concentration of additives all the oils on the market use. Personally I think Red Line oil has a great additive package and is a sturdy synthetic oil if you don’t mind paying a premium for it:

It’s a non-issue that has been made much bigger because of the internet IMHO.

Newer engines have roller cam followers that don’t need much ZDDP. Older engines that are broken in are supposed to be OK with newer oils with low amounts of ZDDP. Problems come up with “performance enhanced” engines with high lift cams with consequent higher valve spring forces to maintain control at high revs. I add a quart of 15W-40 diesel engine oil at each change to my older vehicle for a little extra protection for the valve train.