DIY oil recycling
 

I have a 12v positive displacement marine rated gear pump I have never really used and some remote oil filter heads salvavaged from projects past.
I'm thinking about making an oil recycler with them.
This is limited use recycling, not filter it and put it back in an engine. I will take the oil, scorching hot out of the engine or while still warm out of the gear box and filter it, hot and warm oil is easier to push through a filter.
The only application I can think of where I might take the oil, filter it and put some or most of it back is gear oil for differentials and ATF used in manual transmissions. Since the oil mostly just gets dirty and it's never filtered. Some of the gear oil will be replaced, what gear oil doesn't go back in will just get used as bar and chain oil.
The rest of the oil, used motor oil, mainly 10w-30 and 10w-40, maybe some 5w-40 filter it and use it mixed with bar and chain oil.
I have to use a lot of bar and chain oil here because of the dirt and grit so I use more than 2x normal this could off set a large portion of that.
Any 0w-20, 0w-30 or 5w-20 and ATF along with real dirty black oil from my 6.5L diesel will go straight back to the oil reclaimers.
Even with oil around $50 a barrel, gear oil and bar and chain oil is still priced as if it's near $100/bbl.

I remember an article from a back issue of Mother Earth News that described a homemade filter - essentially three or four rolls of toilet paper - unwound and then rewound tighter around a spindle (sequentially along the length, so the filter was nearly two feet long) and stuffed inside a tube for a tight fit. The reclaimed oil was in a five-gallon bucket above the filter, warmed by an incandescent bulb, and allowed to drip slowly down onto the filter media. Eventually it made it all the way through and what came out was pretty good. They sent it to a testing lab and the lab declared it good enough to use in an engine.

Typical of MEN articles of the time, the whole description was pretty breathless and a bit on the credulous side, but I didn't see anything too far out of expectation with it. It just didn't seem like a worthwhile use of money, space or materials to me at the time so I never went anywhere with it. If you're generating a lot of waste oil however, and have a use for second-run oil that tests good, then such a contraption could pay off for you, especially if your use of the resulting filtered oil would be a once-through application like bar oil.

[edit]
Ha! Found it: https://www.motherearthnews.com/diy/...l-zmaz81jfzraw

The sulfur levels were lowered in gasoline last time they reformulated it, kind of like with diesel.
I'm only interested in reusing the engine oil as chainsaw bar and chain oil. I might reuse gear and manual transmission oil since it mostly appears to get dirty since there is no filter in the system.

There are materials you can add to remove the acid from oil

If you have too much, you could use it for space heating.

I'm not going to burn it.
Limited reuse or take it to be recycled.

Not even using it as fuel for your Diesel truck? Anyway, even though it may not be meant to be used as a gear oil, I wonder how it would withstand reused as a differential oil.

re-purposing used oil? Great. Doing much more doesn't seem worth the effort, not when you know the oil is getting recycled properly anyway.

Filtering and re-using diff/gear lube now...that's a good idea. At least if it's not ancient and contaminated with water and whatnot. Filter something that doesn't usually get filtered and put it back in; done. Rather do that than pay $15 a litre for fresh every couple of years when it doesn't need it.

Any sign of water in the diff and the seal are getting replaced and it's getting new oil.