I've been checking out the EPA requirements for WMO, it seems that the regs want you to have an EPA ID# to transport more than 55 gallons of used motor oil at a time. Additionally, EPA regs on used oil cease to apply when mixed with diesel to be used in the handler's personal vehicles. Farmers who generate less than 25 gallons of oil a month are exempt, as well as "do it yourselfers" (those who come into possession of approximately 800g of oil)
The EPA rules on WMO are: 40 CFR part 279
The rules seem pretty straight-forward, common sense type of stuff. No specific rules for no-no ratio's on mixing motor oil and diesel.
Anybody know how easy it is to apply for EPA identification number? I'm going to look into it!