Yes, your friend was correct.
I use Shell Rotella T4 15w-40 in many of my vehicles. I initial;ly chose it because of its higher zinc content. That zinc content has since been reduced by Shell but it has a little more than other conventional oils.
The higher weight is the main advantage for old engines with greater tolerances between the moving parts.
Last edited by Otto Skorzeny; 04/23/2023 3:14 PM.
