I have a 14 hp lawn mower and I've been pondering what to do when I put it away for the season? It gets an oil change once a year and I'm using a box of old mobil SJ 5W-30 in it. I'm wondering if it would be better to change to oil at the end of the season so good oil was sitting in it during the winter or just leave it and change it at the beginning of next summer. Would it make difference, or am I just over thinking this?