Motor oil leaves a lot of ash behind. I'v seen the injector tips after burning WMO mixed with diesel and they have a lot of fouling. This is the main reason that Detroit 2 stroke engines must use DELO 100 low ash motor oil. If you run the wrong oil like rotella 15-40 it will stick the rings in the ring lands fairly quickly. I'm not sure about ATF but in an automatic transmission when you overheat it you are left with a hard varnish coating on all of the parts. And it stinks. That is why Allison used to recommend 15w40 or 30 wt motor oil in many of their transmissions. MT and HT series showed for heavy / extreme service to use 15-40 or 30 wt. I use 15-40 in mine because I have the hydraulic retarder and it can raise the temperature to 250 while in use. I run it in my AT-540 that is in my International 1600. I'm sure that motor oil or ATF would not go well with diesel heaters.
What kind of two stroke oil are you using? I work with a lot of truck drivers and this old timer came through and swore by adding marvel mystery oil to his fuel.
I use whatever I can get that is TC-W3 rated. Every time I go to Walmart, Tractor Supply or anywhere they sell oil for 2 stroke power equipment and buy on sale. TC-W3 does not leave metallic ash behind. The JASO FC/FD does leave some metallic ash, but costs much more.
lol, whoops, that was a typo. I know chainsaws don't use diesel, I meant to say gasoline, and flubburd my sentence trying to point out that it lubricates chainsaws, so why wouldn't it work for diesel in a bus.