I have a three y-o Simplacity Pro snow blower with a B&S that I usually change the oil on every season. Last season I had an extra quart of AMSOIL Signature Series 0w30 or 5w30 I cant recall but anyway the winter was so lite I think I used it maybe twice for like 45 min each time so I was thinking about not changing it this year good or bad idea? The oil looks like new by the way.