I have been wondering if anyone has experience with mixing used engine, trans, and hydraulic oil with diesel fuel.
You are in the right place now, because a lot of us are making diesel fuel out of just about any waste oil by blending it with gasoline.
My plan is to obtain a 55 gallon drum and filter used oils down to one or two microns and then blend it with the diesel in a transfer tank.
The thing to get right off, is blend your waste oil with gasoline at 10-20% first, then let it settle for 24 hours for WVO and 3 days for WMO, then drain the sludge off the bottom, then filter, then centrifuge.
Are the additives in todays oils harmful to the injection system in my 99 7.3?
The additives in motor oil do not seem to pose a problem for engines or people when burned in a diesel engine as fuel.
Would i need a heater if i run a 50 oil/50 diesel or 60/40 mixture?
Yes, if you blend with diesel fuel only, then your engine will burn your blend better if it is heated first.
Should it be spun in a centrifuge before or after filtering?
If you want to, but proper settling takes care of 99.9% of the precipitates.
Does the oil need heated to separate additives or anything else?
If you blend first, then settle, then you do not need to heat your waste oil.
What kind of mileage and power increases or decreases should be expected, and what kind of savings have you seen?
If you blend properly, then you should see the same mileage and performance of diesel fuel. Most blenders find their blend costs them about 50c per gallon if they are buying gasoline to blend with. Some people occasionally find waste gasoline or other solvents to blend with. Then, the cost is only in filters, and if you learn to back-flush your filters, as I do, then there is only the start-up cost of purchasing equipment for handling and processing waste oils into diesel fuel.