WMO and then some.

I used to work at a Firestone Auto Care place. I am welcome to take as much used oil as I want. I understand filtering it to 5 microns or less, but what worries me is that since working there, I know its not all oil. There's oil, ATF, gear lube, P/S fluid, brake fluid, and some coolant.

I'm not too concerned with the first 4, but the brake fluid and coolant worry me. Would this be OK to burn in a deuce?

Small amounts of brake fluid is ok. The coolant is what you will need to filter out with a water separator type filter.

Wouldn't a water sperator take care of that?

If I suck it from their storage tank in the morning, before the air compressors and pneumatic waste oil pumps come on, the coolant should have settled to the bottom.

I think I may take a sample, put it in a clear bottle, and see how it separates.

Coolant should settle on the bottom. Filter or centrifuge it to clean it. I would blend it 50% with diesel and then ever increasing amounts to make sure you have no problems.

So there should be no danger of the brake fluid eating away any rubber seals or lines?

I won't promise anything but I would be willing to bet you guys change a heck of a lot more motor oil than brake fluid (volume basis) so lets just figure 75% oil and 25% brake fluid, from what I have seen auto trans fluid runs great so no issue there. If you dilute it 50/50 then the mix is only max 12.5% brake fluid in your lines. I would prefilter to pick up all the large trash before you put it in your tank. I use a centrifuge to get the small stuff. As with anything you know your situation and you have to use your own judgement as we are not there to see what comes out of your shop tank. I run WVO in my diesel Benz for over a year blended with diesel, no conversion but I do centrifuge it which seems to remove some of the heavies. I am just now starting to look at WMO for my deuce. I have produced Biodiesel (B100) and plan on using it in my vehicles also.

Another thought is to get a 2 liter and fill it with a mixture of new motor oil coolant, brake fluid Auto trans fluid and gear lube and shake it up to see how it separates. Because the used stuff you get may all be one color. Just my 2 cents worth.

Interesting conversation. Any issues with fully synthetic Mobil 1 WMO? I got a bunch of it I should have taken in long ago.