In 1995 Volkswagen restyled the B3 Passat and called it the B4, but it was built from most of the same stuff underneath. Many B4 Passats have gone to the great junkyard in the sky, because they suffer a perception of poor quality and poor performance, but if your chief concern is miles between fill-ups, this next one is a winner. Find this 1996 Volkswagen Passat TDI here on eBay bidding for $7,400 with 2 days to go, located in Silver Spring, MD.
A big part of the reason B4 prices dropped so quickly is because the B5 was a better car in just about every conceivable way -- powertrain, suspension, interior quality, handling...the list goes on. However, if you value rarity above fit 'n' finish, the B4 longroof with TDI engine is indeed a unicorn with only 1000 of the B4 wagons built in German for US export in '96 & '97. (I couldn't determine how many came with the TDI, but perhaps a reader can enlighten us in the comments).
Under the hood is the old 1.9 TDI, a turbocharged transverse mounted 4-banger that puts out 90 horsepower and 149 ft-lbs of torque. It is going to make that glackity-glackity racket of a classic heavy fuel burner and it is slower than one legged man riding uphill on a scooter, but if you don't mind going slow, you can get 50mpg. Combined with the 18.5 gallon fuel tank you can get almost 1000 miles on a tank before you need to find your nearest green handled pump.
The B4 Passat doesn't have the best reputation for ruggedness or durability, and taking it to your local VW dealer or an indy mechanic will quickly eat away those fuel savings. But, with the help of active user groups like the TDIClub forums, you can do most maintenance yourself and parts prices aren't that bad.
See a car with a longer range on a single tank of gas? Send it here: firstname.lastname@example.org