I need to know the best diagnostic software to all mercedes engines.[/align]Thanks.[/align]

 

All depends on your budget ( £20, £200, £200 or £10000!) and what you mean by BEST.
A £200 "system" will do most things that the mor expensive systems will do so long as you are talking about Engine and Transmission only.
Little difference between systems in this price range since they have to comply with EOBD which is a STANDARD.

EOBD uses a 16 pin trapezoidal socket.
Cars pre EOBD (think it was about 2002/3) use different sockets and protocols.
Stuart