Lubricity of synthetic motor oil is supposed to be the equivalent of dino oil with ZDDP and phosphorus. Don’t know if this is an accurate statement or not.
I wrote to Valvoline several years ago. They assured me that their 10W40 and 20W50 dino motorcycle oils contains both zinc and phosphorus, though they didn’t say in what percentage.
Ester based synthetic oils are suppose to be far superior to all other dino and synthetic oils. Redline ester based synthetic motorcycle oil by weight has 0.25% Zinc, 0.21% Phosphorous and 0.05% Molybdenum.
I also wrote to STP and asked about their zinc/phosphorus content. They replied that STP contains all the zinc, phosphorus and moly that it ever did. Blending one small blue bottle with 4 or 5 quarts of today’s motor oil will bring the anti-wear package up to the standards of the past.
I believe it’s always better to break-in with dino oil. For the first break-in miles you could use Valvoline motorcycle oil blended with STP.
I have an old 72 BMW R75/5 and did this research awhile back to keep the old gal running.
