Is it OK to rotate between full synthetic and syn blend and/or conventional oils? I went to an out of town Walmart and they have Super Tech full synthetic for only $14.36 for 5 quarts so I bought one. Their ST conv is $13.68 for 5 quarts. I have a 5 qt jug each of NAPA SB 5w30 and 5w20. I like ST oil tho I won't need an OCI for 6 months. I just did one a few days ago. And if I do run full synthetic, it's OK to run an OEM, Federated PG241F, or Fram PH3614 filters with it?