I am just getting interested in the idea of burning waste oils (I have been thinking turbine oil (from jet/ turbine engines), motor oil, ATF, compressor oil (if you could get your hands on enough quantity), machining oil, etc.

I have a 99 W210 Chassis E300 TurboDiesel. This should be a good motor for this, as even though it is electronically controlled, it's still an IDI diesel with an inline plunger type injection pump. Being a higher-performance, turbocharged motor, it should be good at getting a clean burn out of whatever goes through it.

Used motor oil is certainly one of the dirtiest things that you're going to come across. Between antifreeze, water, metal wear particles, oil additives (which were good when it was a lubricating oil- not so good when used as a fuel), and soot (especially if it came from a diesel), there's a lot of bad stuff to remove.

Even though turbine oil never discolors (well, if it does, you've got REAL engine problems), you've still got very, very small bits of metal wear in there. The same is likely true for machining oil, compressor oil, ATF, etc.

I'm of the opinion that you're never going to get this clean enough to reliably burn using a filter setup, so that makes centrifuging probably the only real viable idea.

This brings me to the discussion of the small, oil driven centrifuges (offered by the likes of DieselCraft, PA Biodiesel, and others), which it seems most users utilize by running the oil through multiple passes, compared to the larger, gravity fed centrifuges (I'm mostly impressed by the USfiltermaxx units), which it seems most users only do a single pass through.

Aside from just physical size and the amount of G-force thus created, it seems that the larger units are capable of really flinging out antifreeze, oil additives, water, and what not (and, since they are open to the atmosphere, water will flash off and evaporate to atmosphere, and drain the sludge down one drain, and the clean oil down another.

The smaller, oil-fed units, it seems are good at removing soot, metallic wear particles, and what not, but, since they are a closed loop, it would seem that any water or coolant wouldn't have the ability to be removed, as once its flung out, it would just condense and drain back into the tank (since there's only one output).

It seems that those using the oil driven units make multiple passes, while the gravity fed users make only one.

Since the oil driven units need positive pressure in order to operate, which would ideally be created with a gear pump, that if you did have any mayonnaise in the mixture (which ideally should be avoided in the first place, but there's no guarantees of that), that you'd be doing a great job re-mixing all this by using a gear pump.

Conversely, it seems one of the advantages of a large, single pass unit, is that it can be gravity fed, which means you're not doing any further mixing of the contents prior to going into the unit.

Putting all technicalities aside, all I really care about is the end result- we're all looking for clean oil to use as a fuel. I don't care if I have to let the setup run for hours so that the oil can make 10 passes through a smaller centrifuge if that's going to give me the end result that I want.

If I'm still going to have to run the oil through some kind of polymer filter to remove antifreeze and water, that's fine too (since those filters seem plenty cheap).

Since the thinner the fluid is the easier it is to fling out the bad stuff, does anyone mix/ thin their oil down (either with gasoline/ kerosene, jet fuel/ regular diesel/ etc) before centrifuging it? Seems it would lessen the need to heat it?

If the real answer to doing this is to have a large setup, including a gravity fed centrifuge, well, this whole idea may have to wait until I move into a bigger house and get myself settled down somewhere where I'm going to stay for 5+ years.

Any input on this is greatly appreciated.