EDITOR'S NOTE: Many owners of vintage cars with flat tappet Cam Engines may not be aware that recent oil formulations have changed to prolong the life of catalytic converters. This new formulation is now known to cause excessive wear in our vintage cars.
Appearing below are two articles by Bruce Stulzman, a member of the Western Pennsylvania Triumph (car) Association. I also included some options researched from the Internet and from the Triumph Club.
1. Racing oils like Amsoil 20W-50 Series 2000 is one of the oils left with enough ZDDP for flat tappet cams, and one could use special break-in oils but these are fairly expensive and not available off the shelf.
2. Use a good off road synthetic diesel engine oil like Amsoil 15W-40 Marine oil. This oil has the added benefit of increased rust protection which is ideal for engines that are not run regularly an/or are stored. Amsoil confirmed that this oil will work with flat tappet cams. It is not a CJ-4 oil
3. Be warned about Kendall oil. Someone bought the name and simply substituted their own inferior product. The good news is that the former Kendall refinery in Bradford PA is now known as the Brad-Penn Refinery and continue to refine and blend the same Kendall oil under a different name.....Penn Grade 1. Unfortunately this oil is only available from the Coen Oil Company in Greensburg and Washington PA.
4. Other Oils to consider are: Castrol Syntec "Classic" 20-W-50; TWS MotorSport 10W-60 and BMW Long Life 5W-30.
If you know of any other oil to recommend please contact me