Using Mobile 1 oil in vintage vehicles

Question:

Mobile 1 of the recommended viscosity is in my daily drivers, but for my 1950s vintage flat-tappet cars I use Mobile 15W-50 with a nominal phosphorus level of 1200 PPM and zinc level of 1300 PPM. Do you agree it is not necessary to use additives with this oil?

Answer:

Yes. Mobile 1, which is designed for heavy-duty and performance applications such as turbocharged diesels and supercharged gasoline engines, should be fine. The brand and viscosity range of the oil isn’t as important as the ZDDP content when it comes to vintage flat-tappet cars. I don’t want to get into a discussion of the virtues of various brands of oil apart from the zinc and phosphorous levels, because there are as many devoted users of different brands of oil as there are different brands.