thats what I thought your running waste motor oil. if you are going to do that you have to prefilter it to less than 10 microns which is what our stock filter is & run it through a water seperator. Otherwise you get a goooo in the filter that will cause very rough running & in a very short distance shut your motor down. Also do not use more than 5% waste synthetic oil try to only use mineral oil if you do & filter properly blends of over 90% wmo to dino are possible in warm weather.