Adding a NEW lubricant to your fuel to help with lubricity is always a good idea. However, adding a USED lubricant to your fuel to help with lubricitity is not.
The reason you want to run USED motor oil in your fuel tank, is to save money. However, the savings are not pure. You will spend more money and time in engine maintanance. The reason is that used motor oil, or waste motor oil as it is called, will create more smoke, leave more deposits in your engine, and potentially make it harder to start. You will end up spending money on glow plugs, injector pumps and injectors. A new fuel system costs about $1000 (figure a new IP, a set of injectors and a return line kit). Getting the deposits out of the pre-cup, will involve breaking them up with a screw driver. In severe cases, you may need to pull the heads. However, if you run your truck on 80% WMO, you will save about $150 per refuel. Do that 6 or 7 times, and you've paid for your new fuel system. However many refuels you can get out of it after that are freebies.
If you just want to compensate for the junk fuel the refinery sells us these days, then just add some Howes Diesel Treat.