Clearly you've done your research through trail and error (sadly the only real way to do it in PK) and have found what works for you - which is what everyone should do. however i'm very anti-shell, caltex and PSO when it comes to lubricants as there are many alternatives out there which are better and offer better value. BUT your point is VERY valid about the "mistrust" when it comes to other brands as they tend to comme and go like a passing wind. Fuchs & petromin are here to stay though. Fuchs is backed by Hascol, and Petromin is backed by OOTCL so they are able to take the fight to the lubrcation bog boys in PK and they are already doing so.
the biggest disadvantage Fuchs and Petromin have is that they don't sell Fuels in PK so there is no way any pump (except non-franchise ones) will carry their stock.
thanks for your feedback, it is exactly the type of thing more people should be doing when looking for a suitable lubricant for their vehicles.