I'm going on a road trip soon, this will be the first one in my Mazda. How available is 0w-20 at truck stops on the interstates, in case I need to top off? I went out today to buy a couple quarts to bring along and was unable to find any at Autozone or Advance (they have it at the local Walmart so I'll get some there) but not finding it at the usual places concerned me a bit.