I'm runnin 5/30 M1 and M1 filters right now on both my 2001 f150 and my 2000 toy avalon. both cars have 42k. I just switched to syn. plan to Auto-rx both cars at the end of this cycle. It can get down to 30f in the winter sometimes but get up to 110f in the summer. Should I be using 10/30? or somethin else. BTW I love this site!!!!