I hate to necro a thread, but I did WMO in my CUCV.... and I figured I'd share my results. I'm going off of memory from about a decade ago, so I might be remembering things a bit wrong.
I used random oil from friends, that comprised mainly of 5W30 and 10W30, along with ATF and my own 15W40.
I used a 55 gallon drum.. filled about 4/5 of the way up, then added about 10 gallons of gas... I measured what I needed to make WMO85, which is 15% RUG (Regular Unleaded Gasoline) and 85% WMO (Waste Motor Oil).
I then let it sit for a while, before filtering it through a sock filter, 3 spin on filters, then another sock filter, all progressively smaller.. 100, 30, 10, 2 micron, it then went into a smaller 5 gallon container where it was put through a .5 micron filter into the fuel tank.
I tried filtering the oil by itself, and it failed miserably. The gas thinned out the mixture quite a bit, allowing it to filter faster. If it wasn't thinned, it would not filter very well.
After adding the gas, and letting it sit, there was a noticeable color and consistency change in the oil, for the better.
I was able to run about 50/50 WMO85 and diesel, before I started seeing performance issues and smoke. I did try 90% WMO and it didn't like it...It ran, but very little power, and gobs of smoke. In winter, I could do about 25% WMO85 before I started noticing some minor issues like hard starts/longer cranking. I tried running 50/50 in the winter, and it was an absolute pig, and didn't wanna start.
Overall, it was a huge success. Diesel was over 4$ a gallon, and I was able to bring my fuel costs down to a little over $2/gallon.
There is one thing, that I didn't anticipate, that messed me up.
Oil, and ATF, have HUGE amounts of additives designed to keep things clean, called detergents. This is designed to reduce deposits, and, well, clean things up. Guess what it does to a gas tank that's 30+ years old that's never been cleaned out? It cleans it out.
In your first tank, you WILL have every piece of gunk, crap, and chunk that's in your tank, in your fuel line.....
I think I made it 100 miles on my first 50/50 WMO85 fill up, before I had realized I was losing a TON of power.. I pulled over, pulled out my phone, thinking I screwed something up, and one of the first things I saw was 'It will clean out your tank, carry a spare filter or 3'.... So I swapped the filter, and was back on the road.... It happened again about 200 miles or so later, to a much lesser degree, and swapped the filter again.... but never had an issue after that.....
So.
Mix 85% oil with 15% gas.
Let it sit for a month or more.
Filter properly, preferably in stages.
Carry spare fuel filters.
Mix 50/50 with diesel.