I have an '04 honda and it specs 5w-20. I want to buy the oil in a 5quart jug but stores usually don't carry them in that size so I was wondering do any honda owners here use 5w-30 in there engine that specs 5w-20? Have you noticed any adverse effects? And does anyone know exactly why honda specs 5w-20 since most new cars use 5w-30? with the exception of ford. thanks.