Youve been told wrong. 20w50 is way thicker than 10/30 and used more for higher mileage cars, trucks and suvs. In colder wheather, thinner oil makes it less harmful on the engine, but thats what it is thinner oil. 10/30 will be fine, it is a honda. In my blurboed cars, I uses 15/50 just cause of the heat factor.