From your mechanics recommendation it appears you have a flat tappet cam in your engine and needs an
oil that has
Zinc and Phosphorus (ZPPD) additive.
As Mark IV wrote the Delo
oil does have the additive but needs an Anti-foaming agent. Delo 400 MGX 10-40 with ISOSYN does have the Anti-foaming additive.
https://cglapps.chevron.com/sdspds/P...&docFormat=PDF
I use Valvoline VR1 10-30 racing
oil (conventional) with ZPPD even though I have a solid roller cam. (I like their oil).
If you need more info I'd just do a Google search as this site, and every automotive forum is littered with "Dead Horse" threads on oil recommendations.