[Zero10]

Don't do it.
ATF is NOT ashless, and it will lead to increased piston deposits and possible other side effects down the road, like injector clogging.
If you want to keep your fuel system clean then use a can of lubro moly diesel purge every year or every fuel filter change. You run the engine on straight diesel purge until the can is empty and it has been reported on TDIClub to do some really good things for injectors.

As an every day additive I usually use either ashless 2-stroke oil, power service or stanadyne. All 3 will grealy increase the lubricity of the fuel
Or, the old mercedes diesels take very well to alternative fuels. You could run any blend of biodiesel and it will only do good things.