I've been considering for some time just periodically changing the filter and topping up the oil on the older cars and lawn mowers I service. This would include my Roadmaster, my grandmother's '93 Dodge Caravan, and my brother's '03 Pontiac Grand Prix for cars and 3 Craftsman YTS 3000 42" riding mowers. For the Roadmaster filter changes would occur every 4-5K miles, and the Caravan and Grand Prix once a year. Two of the mowers would get bi-yearly filter changes and one once yearly, as it sees more use in a mowing season.