I am curious to know how often everybody changes the oil on their mowers. We have a QuikTrac with a 19hp kawasaki and have to change the oil and filter every 25 hours. This seems to be a bit excessive to me but maybe it is not. The owners manual says every 50 hours but that is too long. Every 25 hours is 1x per week so you can imagine the costs add up over a year. Is it the Kawasaki motor, or are all mowers that are run hard 4 days a week like this?