So I know ford back sped'd the 4.9 ford to 5w20 motor oil, but there shouldn't be much of a difference between 0w20 and 5w20 should there? Reason I ask is I am using the mazda Idemitsu Ow20 in my mazda and I could use just one type of oil and keep it in my inventory. What do you think? would 0w20 be too thin for the old 4.9? I have been using 5w20 with good results.