[Tinker]

I used to only use straight 30 diesel in florida. Mn I use 10-40. When it's hot you see a bit of drop. But nothing like going from 80 to 20. Or an increase really that drastic either. Maybe with the thicker oil overall over 5-10 psi. Hot.


Standard Flatheads are a low oil pressure system. If you are above 0 hot you are okay really, 10+ better. Ya high pressures rush oil over bearings to my understanding. Old oil can be abrasive.