The U.S. version of the BMW 5 Series spans six model-year generations:
E12 - 1975 to 1981
E28 - 1982 to 1988
E34 - 1989 to 1995
E39 - 1997 to 2003
E60 - 2004 to Present
The first of the rest-of-the-world E12s was the wheezy 1.8-liter four-cylinder carbureted 1974 518. Using a four-speed Getrag manual gearbox and a 4.44 differential, the first 5er provided competent and durable transportation in Europe, Asia and the Middle East. Naturally, it was far too underpowered for the U.S. market.
Other models that didn't make it here include the 518i, two 520s--one with an M10 four-cylinder and one with an M20 six-cylinder, a 520i six-cylinder, carbureted 525 and 528 models, a 528i, and the spectacular bespoilered 218-bhp M30-powered 1980-81 M535i. In the U.S., we got the 530i starting in 1975 and the 528i in 1979. Both are powered by "Americanized" versions of BMW's venerable M30 sohc six-cylinder engine. Heat problems caused by EGR equipment on the 530i caused cylinder head failures, resulting in many replacements and a great deal of desmogging. Other than that, the cars are very hearty.
The E12 5 Series represents a tremendous bargain on the used car market, especially if you can find a well-maintained example. BMW has an ample supply of parts, and performance bits are out there as well. While the E12 isn't everyone's idea of a garage mate, they do have a great enthusiast following. Check out www.firstfives.org to meet them.
The E28 5 Series also saw myriad rest-of-the-world engines that never made it here. Only five versions of the E28 did arrive in the U.S.--the 528e (1982-88), 533i (1983-84) 535i/is (1985-88), BMW's sole diesel-powered U.S. car, the 1986 524td, and the mighty 1988 M5.
The 528e was powered by one of two versions of BMW's M20 "eta" 2.7-liter sohc engine. The 533i and 535i both had the big M30 engine, and the former was the fastest four-door sedan sold in America in 1983. The M5 was, of course, a completely revamped car with few motivational parts shared with its lesser siblings. The E28 has a well-deserved reputation for tank-like build quality and durability, with ample room for people and cargo, and a sporting nature that belies its conservative appearance. It is also the last of the traditional "boxy-shaped" 5 Series Bimmers.