Welcome to the Energy Matters Forums Blownoiler
Thankyou for the welcoming manner Gordon!
I reckon you'd have to filter it pretty well, as it contains a lot of extremely fine metallic particles and soot, etc, which would surely cause increased wear to the cylinder walls, and especially the injectors.
Good points, generally the folks running U.M.O. (used motor oil) run the oil through a centrifuge (expensive to purchase) and over strong magnets to get a reasonably clean end product, probably the cleanliness of the collected oil has a big impact on the final filtered product, so I would be looking for cleaner oil to work with rather than the black engine oil that comes from my own motors sump. I don't think that the cylinder wall wear would be impacted greatly as the drained used oil was probably still doing it's lubricating duties up until it was drained at service time, and as diesels run excess air in the cylinder I am led to believe that there is a cushion of air between the burning air/fuel mix and the cylinder walls during normal operation, but then I don't know for sure.....I'm guessing that there is minimal fuel to cylinder wall contact as diesel engines generally have a long service life. Obviously with newer engines the high injection pressures (up to around 30,000 psi) really put the injectors under the hammer, but this early mechanically injected engine runs a mere 2100 psi, and a set of injector nozzles runs into a few hundred dollars rather than a few thousand that newer injectors can cost.
This would take a fair bit of energy to perform. It would be rather more viscous than diesel or vegetable oil too, so would perhaps require a fair bit of pre-heating before injection.
yes, no doubt the used oil would contain not just engine oil, but gearbox/diff oil as well, so its viscosity could vary somewhat from batch to batch.
As far as environmental soundness, you have to compare it with what would otherwise happen to it. I thought that used engine oil was recycled in some way, and some fraction was recovered for use in oil products, but I haven't investigated this subject lately.
I haven't done a lot of research on what happens to used motor oil, so am only putting forward what I have been told (and what I wanted to hear
), yet have heard of "remanufactured engine oil" being sold in automotive stores, which reminds me of what I was told back in the early 80s regarding one of sump oils uses, which was to spray it onto dusty dirt roads in order to seal the dust somewhat!