98-99 has a mpg gauge. It's simply a vacuum gauge. Useless.

Buying an S Class? What do you care about fuel economy?
Would you look at the read out and drive differently? I doubt it.

A W140 (96-99) may prove to be very sorted out, and reliable.
I shudder to think about what could go wrong ($$) with the first
year of a new model S class (2000) out of warranty.

Steve
'97 S320 as of 3 weeks ago.