A school in Utah is selling 57,000 gallons of heavy heating oil at an on-line auction. Bidding starts at $1 a gallon, for 1 gallon or as much as you can haul away. I don't know if this stuff can be doctored down enough to burn in our trucks, but here is the DTR link:

https://www.dieseltruckresource.com/...s-t268252.html

 

The pour point is 90F or higher.
Sounds like #3 bunker oil, the stuff is like tar at room temp.
It's usually heated before use.
You could probably cut it with #2 to thin it out.

I personally wouldn't want to mess with it even if it was free.

 

The stuff has to be heated to pump it. The tanker you put it in can't be one that hauls regular fuel or gas. It will ruin it. The stuff is like tar. If you leave it in the tanker too long and it cools off you have a hell of a time getting it out. A heated tanker would help.

I don't think you want to put it in a cummins unless you have something to thin it with. An asphalt mixing plant can use it.