Before I process my oil, I put an old tee shirt in the filler hole in my 330 gal poly tank, dump all the stuff in the hole. Not sure what filter rating to apply to the tee shirt, but it sure does grab a lot of poo. So far most of the oil Ihave collected has been coming from word of mouth, people dropping it off at my house, bringing it to work and then putting it in the trunk of my car. I have collected about 75 gallons that way. So far I have just been collecting for a few months. The big score comes this thursday, I will pick up 275 gallons but I will have to pay for that @ around $1.00 per gal. Keep in mind I am also heating the barn with WMO.
The cleaning process will still use the centrifuge though. Both for the deuce @ 75/25 ratio. 75% WMO.
When burning the WMO in a stove, the centrifuge really helps to keep the ash down, and pulls out a great deal of the stuff you really didn't want in there to begin with.