Worst: 1986 Chevy Blazer, at a whopping 4.6 MPG
Best: 2004 Honda Insight - average 58 - 62; best full tank average was 74 MPG.
Honorable mention: 1987 Toyota Camry, which got 25 - 28 the whole time I drove it (200K miles or so) and is still on the road (at 400K miles or so) and running at about the same efficiency.
Best: '90 Chevy Cavalier – 32 mpg, uphill, downhill and sideways, city or highway. That POS was almost, but not quite, a great car.
Worst: '72 GTO with a 455 & six-pack, racing – 6 mpg. So-called “Normal” city driving, it got a lot better, say 10-12 mpg. I loved that car.
Worst : '80 3/4 ton Chevy pickup, 6 mpg with a/c, 8 without. Only thing I didn’t like about it.
Best : '96 Triumph Tiger, 42 mpg. Wrecked it pretty good 2 weeks ago, might fix it if I can find used parts, the cost of new parts would be about twice it’s worth (and I get a discount).
Worst: 1988 Ford Thunderbird oval track stock car, about 2.5 miles per gallon. For a vehicle driven on the street, it was the rig I used to tow the race car, a 1987 Chevy C3500 one ton dually with a 455. It got about 7 mpg unloaded, 5 when pulling my 26 foot enclosed trailer. It held 80 gallons of gas and it was not unusual to use up that and more on a weekend.