will it hurt?
 

Will running 10w30 synthetic hurt our engines?

well it was designed for 5w20. Why not just use it?

im assuming your have an "2004 two door", its still a new car and i would stick with 5w-20. i myself use 5w30 and i drive in cali weather.

so unless your FI/built, i would stick with 5w-20 or you can try 5w-30/0w-20 under certain conditions