THIS ARTICLE IS A GOOD READ:
There is *no* advantage to adding motor oil, or transmission fluid to diesel fuel. Period.
There are disadvantages to doing this however, including damaged injector pumps (especially with turbo diesel electronic pumps), clogged filters, etc.
The manufacturer of our injector pumps strongly cautions against using either when their pumps are used.
There are many additives that are approved, and are in fact *much* cheaper than either motor oil, or transmission fluid. As an added bonus, these additives really work!
Most diesel fuels and engines don't need additives, but if you feel the urge to pour something else in the tank besides diesel fule, use a product that is *specifically designed for the purpose*.
Kerosene is added to diesel fuel by some suppliers, though in small quantitites. Kerosene has virtually no lubrication qualities--adding more (and an essientially unknown amount, since you don't know if or how much has already been added by the supplier!) is a sure way to cut the life of your injector pump. Kerosene is routinely added to home heating oil, in large quantities. The furnace doesn't know, or care. The furnace oil pump does not have the same clearances (they are more crude, greater clearances, lower pressure...) and the kerosene won't hurt them. Most will (and often do) run on straight kerosene--here in NH, if the oil tank is outside, the mix will be either 50/50 or straight kerosene. Kerosene doesn't have the same heat values either, you won't get the same amount of power from a gallon of kerosene as from heating oil, or diesel fuel.
#2 diesel fuel is basically #2 heating oil, with the exception that rather than adding kerosene the supplier will add an anti-gel additive. Costs more, but then it sells for more. In the summer, there is virtually no difference, other than legal issues. (again well debated).
A wise owner will add nothing to the fuel tank that is not designed for the purpose. People who pour whatever they have at hand (motor oil, atf, gasoline additives (yes, some do!)) simply add to the profits that repair shops (such as mine) make. It is a big buck job to replace the injector pump, you dno't want to do it any more than necessary.
NOW IF YOU BELIEVE THIS OR NOT IS A DIFFERENT STORY.