I run a 5w-30 in my Jeep 4.0. I just passed 215,000 miles and it doesn't use a drop of oil. 4000 mi oil changes. These motors also like 40W. Recently I sold 3 of my 4 motorcycles and have a remaining stash of Castrol 4t 20w-50 motorcycle oil (43 quarts). I am moving and would like to whittle this down some. What do you think of mixing 3 qts of 5-20 conventional with 3 quarts of the 20-50 mc oil?