Do note that the poster asked about a 20W50 oil, as far as i know caltex havoline in 20W50 is an API SG grade oil so it can't even be compared to an API SL. Anything below API SH is obsolete now and should not be used in anything less than a VW beetle or morris minor.
As far as the best engine oils go, in Pakistan there is nothing better than Mobil1 super syn 5W50 and Zic XQ. both are top (synthetic) performers and no other oil comes anywhere near them.
As for mineral oils, only Fuchs Titan Super GT and Petromin Ultra7 (both 20W50) offer decent calue for money and are both available in API SL.