M119s (V8s) are a thousand times MORE reliable to M104s (L6). I can personally testify on this comparing my S with my E 320 T.

Having a good friend with a SWB S 320 to compare at (same year as my S 500 L), I can also assure you that the LWB has considerably a much better ride. On highway trips, the V-8 matches or even betters the L-6 fuel consumption. On town driving is another story...

But, generally, a well maintained W140 should be as reliable or even more reliable than any other M.B., including the W126 and W124.

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A. Rosich
CL 500, 1998
S 500 L, 1998
E 320 T, 1995 [Sadly sold ]