Hey, Tonkovich,

My W126 was the 420SEL, a slightly smaller motor from 1986. I tended to get 19-20 overall, with a good deal of highway in the mix, when I lived in Denver, CO; and more like 17-18 overall with a lot of city in the mix when I came back below sea level to New Orleans. Mine required premium, too (weren't there some exceptions to that in the Benz lineup prior to 1986? People here will know).

But if it does require premium, you need to use it.

I seem to recall that I got about 24-25 highway (at about 60-65 mph) during the long trip back from Colorado. But the car was well loaded down: I was toting two suitcases, a back seat full of clothes, and Miss Linda's cat Marie-Antoinette in her carrier.
.

__________________
* *
-- Paul W. (The Benzadmiral)
('03 Buick Park Avenue, charcoal/cream)
Formerly:
'97 C230, smoke silver/parchment; '86 420SEL, anthracite/light grey; '84 280CE (W123), dark blue/palomino