I switch from 20w50 to 10w40 in mehran after 15 years and found my car is running smoother on 10w40. it reduced the engine sound, my car was giving the smoke at the cold start in the morning but after switching to 10w40. the problem got resolved. on 20w50 she was reducing more oil. Was using 20w50 before because mechanic said once to my father that there is not a match of 20w50 in any car.
After I switched to 10w40, i went to the mechanic and tell them that this has happened. Tell me why its more smoother on 10w40 and he has no words and concluded. "10,40 ap ki gari ko rass ageya hai".
I have only changed the grade no the brand. And I will suggest you to go for the same brand but new grade oil. If it wont suit to your car you can changed to 20w50. also change the oil with a warm engine, not cold engine.
Good luck!