GT40 oil viscosity

[gary s]

Another important thing to remember is that Ford stopped any development work on the Windsor engine last century . Somewhere right now someone is working on a new synthetic formula,do they test it on every engine ever made,who knows. The idea of synthetic's anyway is extended oil changes. Your in the wrong hobby if your trying to save money

[Jonny Quest]

all I said was that was what I heard. just relaying info, not saying whether it is right or wrong
something about the "tappets" and not enough zinc in synthetics.... I don't know.

Many oils today — synthetic and Dino — don’t have high enough ZDDP for flat tappet engines. That may have been one of the main reasons that PCM wasn’t too keen on synthetic oils, fearing that people would jump to synthetics and forget about ZDDP. Generally speaking, the diesel oils and the “racing” oils are the most likely options to have sufficient ZDDP content. So, if you run a flat tappet engine, look for a ZDDP content be be no less than 1,200 ppm…or just buy some ZDDP additive and open up your oil choices.

JQ