Can used hydraulic fluid be used as diesel fuel or to supplement? I have somewhere around 200 gallons of it, but I don't know if it is safe.

 

I've ran a gal per tank (new oil), and after 3 tanks, I had to run Howes Meaner Kleener to burn off all the crap it leaves behind. If it's used, don't run it. Too much crap in it (metal, rubber, and other small particles) to cause excessive wear on your VP and injectors.

 

The hydraulic fluids we have are very aggressive on rubber. Thats the reason for running Teflon hoses.