easy! get waste oil.......filter oil......cut with diesel. fill tank

you want to stay away from synthetics though, they don't burn very well. WMO doesn't need to be heated. WVO needs to be filtered well and heated.
I just rigged myself up a quick, mobile around the garage filter station. use a $5 Princess auto self priming drill pump. I got from work a primary filter head from a 16v-2000 Detroit diesel. uses the primary filters in parallel (by virtue of the head design) at about 40-50 micron nominal rating. Just a big prefilter. then went to NAPA and got 2 fuel filter heads with 2 micron absolute filters i piped them in series. spent about $80 for parts. Oh the hex head plugs in the blocking ports on all the filter heads are magnetic NPT drain plugs. with the el-cheapo 3/8" drill wide open it pumps a 5 gal pail in just a couple minutes.