I seem to have a preference for M1 for no apparent reason. I got a great deal on some PP that I have in the garage I will most likely use in the Subaru but could also use in the Nissan. It is convenient both my vehicles use the same filter and grade of oil however I have been using M1 in the Nissan since 7500 miles (last free OC from dealer. I know the better oil most likely is what ever is cheaper between the two but why do some of us prefer one over the other?