Get a 1994-1996 Cadillac Fleetwood, Buick Roadmaster, Buick Roadmaster Wagon or Chevy Caprice (with 5.7 V8). I LOVE mine, I get around 20-23MPG (peaked once at 26) in my Fleetwood, it's a tank. Longest car since the 70's, I picked it up for $2300 with 123k on it. The only thing equally luxurious (short of a Rolls Royce) is a Lincoln Town Car.
The wagons demand a premium in price, as do the Fleetwoods, as they're SUV-big with a luxury car ride. If you tow, keep in mind, with a towing package, the Fleetwood was rated for 7000lbs, they all came with the same drive-train (as did the Corvette from 1992-1996). They all come with climate control (except the Caprice), they call come with power everything, most (all Fleetwoods) have leather & heated seats.
Or... get a used Town Car or Grand Marquis. SUVs are for soccer moms, FWD econoboxes are for kids.
ETA: www.carsurvey.org
You won't find a bad review of a 1994-1996 Roadmaster/Fleetwood/Caprice