@shqamar
So its confirmed that noise is coming form the buckets aka hydraulic lifters?
Also if you give a lot of raise does the noise vanish away? If yes then maybe oil pump issue.
Whats the reading on oil pressure gauge? Is the pressure low? are you facing oil pressure issue? Is the car running cold without autofan and thermostat? Is there too much sludge now in the engine? 10W40 oil is runny and if oil pump is in good nick, it should have no issue oiling well those hydraulic lifters. Why don't you open the head cover and check with a stick if any of those are pressing softly. Its not very costly to replace them anyways. I think they would cost 3 to 4K for a full pair of 6 of them. Just get the original Japanese ones.
Eik sasta totka: Flush the engine with STP on your next oil change, pour a can inside, let the car idle for 15 minute. (idle means idle, if you drive the car with STP in it, it will ruin the engine) and then pour 10W40 and let us know if the noise is gone?