You can use what ever oil you like. Honda recommends not require that you use 5w20. The oil grade would depend on the area that you live. If you live in the desert I would recommend 10W30 or 10W40. In Cold or normal conations 5w20 or 5w30 is fine.

I have a 99 Accord I4 and it recommends 5w30. I've used both 5w20, 5w30 and 10w30 in my car and I don't notice a differents in gas mileage