Here is one man's opinion: You need to have zinc for flat tappet cams. They took out the zinc compounds that they used forever out of oils because it damages catalytic converters and all new cars have roller cams and don't need it anyway. Use regular brand name oil and add a zinc additive product. Regular passenger car oils have detergents and other additives which is good. Add the missing zinc and you are good to go. Diesel engine oils have too much detergent. Racing oils don't have enough detergent. This is the information I have gathered from much reading on the subject over the years.