FILTER, FILTER, FILTER!!!!! aim for 10-20 microns. dont try to filter it all at once, work your way down to a smaller number. I have a 16 on my garage pump and a 10 on the truck.
From the sounds of it your oil is sitting still in a barrel, thats good, Best thing to do is let it sit in a hot building or the sun directly and let it gravity settle as long as possible, 1 week or more. Suck the good oil off the top and push it through a water trap fuel filter. I prefer the Golden Rod clear housing with replacable filters just so I can see whats in the filter. People say the water trap ones are a waste but more then once I have gotten a bit of water I didnt realize was in the oil and the filter stopped flowing, so it did its job, I think they're cheap insurance.
The bad thing with WMO is the high carbon count, carbon doesn't burn, it's SUPER hard and will score almost anything it goes through. if it's diesel oil there is ALOT of carbon in it, the blacker the oil, the more carbon. if it's gas oil it's got lots of corrosive stuff in it, that's why gassers use a PCV, they develop lots of weird toxins the cranckcase, which gets into the oil.
at the rate your using it I don't think you will have any problems immediatly but I would be cautious. I have not experimented with centrifugeing WMO yet, I have everything just haven't tried it yet to see just how much carbon it will sling out I think if you got the carbon out it would burn alot better.