Mercedes Fuel Economy?

[GradyService]

I want to start by saying that I love my 560SEL. I just don't love the 15 mpg. I have done everything in my power to bring up the MPG. It has came up a little, from 12 when I bought her, to 15 now that I have replaced Plugs (w. Bosch Platinum 2), Wires (Bosch), Air Filter, Smog Pump Filter, and cleaned the cap and rotor. I am keeping the car, on that there is no question. I was wondering, though, what do you think of something like a
190E, or 300E for a running around car. Not a especially late model piece, something from the 80's or early 90's. What kind of mileage should I expect? And are they pretty reliable?
Thanks, God Bless,
Dave.