From your original question:

There is absolutely no difference between short and long wheelbase in terms of reliability or any other issue besides the extra legroom at the rear seat. If you carry often passengers on the rear, then the extra room might be a plus. Some W140 owners say the long wheelbase has a slightly (but VERY slightly) better ride.

The S 320s also have a five-speed automatic.

The L6 engine size and power disadvantage is offset a little by the higher rear differential ratio compared to V8 W140s.

And like any of the members have said before, always buy the latest model towards the end of production and with the fewer mileage. A detailed service history is also a must!

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