I was going to mention mixing in a little gas. I always add gas to my WMO, mainly because if any water is mixed in the oil it helps to separate it and let the water settle to the bottom. A little gas mixed in will also help with your fuel pump. I won't run straight WMO because I don't want to burn out my fuel pump.
Yes, I too find gasoline is very effective at removing water, and radiator fluid from motor oil. It also seems to make the dirt fall right out, if there is enough gasoline in the blend. The carbon is the hard thing to get rid of, because its density is so close to the specific gravity of motor oil that it can take months for it to settle out with gravity alone.
I've basically been getting a bunch of used motor oil from friends and neighbors, along with a little stale gas, and about ten gallons of clean fuel oil taken from a tank that was being removed from a house. I've thrown in some old diesel treatment left over from when I had a Cummins Dodge.
I have about 150 gallons of WMO, a couple is gear oil. So far I've filled up one barrel (55 gal) by running it through a 100 micon screen into a funnel with a doughnut magnet. That's what's been sitting for about a year. (like I said, been a little busy) I'm planning on building a rack in the next week or so to hold 4- 5 gal buckets with 10, 5, 1, and 1/2 micron sock filters to gravity filter. I'd like to try and put a heat blanket on the barrel to have the WMO fairly warm, (above 100 degrees) so it flows better. I've got two hand pumps, one for the first barrel, and a second for the finished product barrel. The 5 gal buckets will have an ABS or PVS bulkhead fitting in the bottom with a valve, and a 4" cap in the top lid to hold the filter sock. I'll do 5 gallons at a time, maybe 10-15 gal per day. I'm in no big hurry as I'm restoring my deuce and it's not road worthy right now. Any thoughts on this set up?? I may add some more gasoline, but not 20% as I probably won't run WMO at more than 50% in the fuel tank.
Sound like a nice waste oil processing system you have made for yourself. I also process in 5 gallon batches because that is how I get my waste oils, and I like to see the oil stream as I am pouring it from one container to the next, because I can see the dirt layer through the pouring stream, if I am careful.
I use a fairly coarse screen to start the cleaning process with, which is about the same mesh as a common kitchen screen/bug screen, which I thing is something like 500 microns. That gets the leaves, bolts, parts, etc. out of WMO, and the french fries and corn chips out of WVO without that stage taking hours or days.
I then pour enough gasoline on top of the coarsely screened waste oil to make it 20% of the whole solution. I find agitating the blend does nothing. I then leave it to sit undisturbed for at least 2 weeks for WVO-blends and 2 months for WMO-blends. After the settling period, then I pour it again carefully into a blending tank And, again I watch the pour stream very carefully, because I can see that there will be dark and/or thick fluid at the bottom of the bucket, so I stop pouring when that dark and/or thick fluid at the bottom starts coming through.
I have a 20 gallon blending tank, so I leave the 20 gallons of settled blend to sit together for 2 days, then I extract a sample from the top and one from the bottom, to make sure it is uniform, which it typically is, except in the cold. I also examine the bottom sample for any additional sediments. At this time I keep drawing off the lower sample until it runs clean.
After the 2 days of additional settling I use compressed air at about 5 PSI at the top of the blending tank to push my blend out of a valve at the bottom of the tank through a line that goes to a series of filters 250-micron, 100-micron, then 1-micron. For settled WVO-based waste oil blends that is all I seem to need.
WMO, is another issue. It either needs to be settled for 2 months, or centrifuged about 10 times to remove the carbon.
If carbon is not removed from WMO, then it will result in coking your engine.