You must have very deep pockets to be able to afford using a Mercedes V12 car as a daily driver. Think about the serpentine timing chain. On the V8 cars it needs changing at around 100k and is really expensive. Weigh this along with the general tendency for the V8 and V12 parts and maintenance to just be much more hateful than the sixers. A PPI from a really good Mercedes man would be worth the expenditure.
Otherwise those V12s are awesome! Really smooth and swift. Don't expect much economy. Just jack the price of everything up to twice what an inline six car would cost and you would be in the ballpark. Harder to DIY as well, you'll be more dependent on your indy so make sure he's a good one. I applaud your effort to even investigate owning such a beast.

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'02 BMW 325i
'85 300D 450k
'93 190E 2.6 170k(killed by tree)
'08 Ducati Hypermotard 1100S 6k
'06 Ducati S2R800 14k(sold)