bizarre dash on 300sdl
 

1992 300sd on ebay with a current price of $8600 shows a dash with a mpg
gauge on it. Can that be? MPG gauges (actually vacuum gauges) are a function of manifold vacuum, not present on diesels. is it a real diesel dash?

I see it has the glow plug light on the dash too but huh!!

Do you mean this one?
 

I wouldn't be surprised by it. I'd expect everything related to that on the W140 chassis to be electronically controlled.