mixing oil
bought a few cases of valvoline racing oil(v-1)with the good supply of zinc in it. i got 20-50 and i will use it in my drag car as is, but i have a 408 SBC with about 525 hp , built for the street with all the good stuff. the engine builder says 20-50 is overkill (too heavy) and i should use a 10-30 weight. what do you guys think, and if it is too heavy, can i mux a lighter weight valvoline race oil(same stuff) to thin it down a bit. any ideas what weight to use and what will be the end weight of the oil if i mix it up thanks chevy art