i have a quick question for you guys. thought i would just ask in here so i dont have to make a new thread. what is the best oil to use in a high mileage ka?

got this form NICO:
"The best oil I've found for the 240 is Mobil 1 0W-40. Simply awesome. I was using the 15W-50 before, but the car felt sluggish and the valves had a nasty habit of tapping until the engine was VERY warm. The lower weight oil worked wonders. Revs faster and smoother and no more valve tap!! "
has anyone ever used mobil 1 0w-40? cause my motor does what he explains what his car does. just getting some input.