Classic/Antique Car Repair: zddp, piston ring, copy performance

Question
Hello:  I've heard that since the EPA is removing zddp from motor oil, older engines with flat tappets could suffer from rapid wear.  Should I avoid using the latest API SM oil in my flathead Mercury?  It's a stock 255 ci '53.
Thanks.

Answer
The EPA has moved to remove all or parts of the Zinc additive from motor oils as if it gets my the piston ring as it can poison the catalytic converter. However the current motor oils are so far superior to the motor oils of old that the removal should not hurt the lubricity of the current oils, even for non roller equipped engines. Careful reading of the advertising for the additives sold on the market almost all include somewhere in the copy "performance engines". It appears like the leaded fuel additive scare that was going around a few years ago that the use of these additives is almost mandatory if you are drag racing the engine or using it in a tractor to plow potatoes. But under the normal light duty use that most antique and classic cars are operated under the current fuels and lubricants will due just fine. A case in point is a look at the way back machine, in the 50's and 60's we ran Amoco unleaded or Blue Sunoco in our rods and racing engines and they lived just fine. The key word in the use of the engine, commercial  hauling, racing, or marine, or just plain old car cruising. Just my humble opinion. I do not use any of these products in any of my old engines.