Would you pour ZIC XQ in a brand new Mehran?
It's not about engine condition. It's about engine demand.
Newer oils- i.e. SM, SN- are not designed to protect old flat tappet designs. And most of them in the market are not backward compatible to protect SL, SJ spec'd motors. In fact, IIRC only Mobil 1 and Mobil 2000 are backward compatible. And while Mobil 1 is an over kill, Mobil 2000 has pretty much the same specs as nice Diesel grade oil (Delo Gold or ZIC 5000), so why not the cheaper option in first place?
Delo Gold and ZIC 5000 are about 2000/4 litre. Mobil 2000 is about 3000/4 litre.
Rest is up to you. People do pour ZIC A+ in Mehrans and fill them with HOBC, expecting some miracle.