Almost no one has the discipline to truly drive with a light touch at every stop/start, and to truly drive 55mph on the hiway day in and day out. If you do, then 16-18mpg is do-able. :meh:
That said, my 92 seems to get a couple miles less per gallon than my 91, even though they're both stock.
I drove my stock 91 across the country, round trip, for three summers in a row back in the late 90's. Highway mileage was consistently between 17-18mpg.
BUT: That was taking it MUCH slower than most folks are willing to drive. I literally NEVER went above 55-60mph.