replied ur PM. copy pasting it here for other members too.
Sorry for not replying to ur query. actually just a day or two ago someone ask me the very same question n though it was you, n that u wanted opinion from other members.
anyways, sir, the rule of thumb is, never touch anything that is working fine or doesnt need to be changed or u are satisfied with. cars sort of get tuned to the engine oil u use with time n thats why its not usually recommended to change the oil grade or brand so often.
having that said, zic yellow one is Zic hiflo, 20w50, its a heavier oil n its recommended for older cars with more mileage. are u the first owner of ur car? r u absolutely sure that the mileage is original? if yes, then u SHOULD be using havoline formula 10w30. 20w50 for a newer car n that too in winter is too much punishment for the car. n 5000kms drive is also too much. thinner oils usually have longer life. i use 20w50 havoline n change it at 3000kms max.
Now its totally up to u, if u feel that the car is fine. dont switch the oil. if u are willing to take small risk of may be falling rpm etc. take the risk. but make an informed decision and once u take the step, stick to it.