I have a couple of quarts of Mobil 1 Extended Performance 0w20 saved for my next oil change. I was gifted a couple of quarts of Mobil 1 ESP 0w30 by an acquaintance (BIG SURPRISE). I'd like to combine both oils when I do my next change. While I doubt that there'd be a problem in doing so, I thought I'd ask here just to be sure. Thanks!