I was reading the engine owner's manual this morning to my new mower (I know......I was just looking for something to read while doing my morning business) and it said change oil first 8 hours then every 100 hours after and change oil filter every 200 hours. I really don't like to go more than about 50 hours between changes but I change the filter every time. Don't make much sense to me to put clean oil in and leave a dirty filter and whatever oil is in the filter is dirty too? How do you guys do it?