Hi guys,
I have been running my diesel car (MB300E TDI '94) on A1 for about 75000 km now. without 2 stroke oil, and without any problems whatsoever. I too was recommended to add 2 stroke oil when I first started doing it , but I quickly discovered that all it did was to clog the nozzles. I do belive though, that it is dependant on the engine make and model, I have seen a '88 golf dielsel give up, ok it was a ramp vehicle so it was NOT maintained.
Brgds
Doc