When was the last time you thought about the Volkswagen Passat? I’m guessing it was a long time ago, if ever. The Passat is one of those cars that melts into the background, going about its business quietly, competently and completely unnoticed.

But it’s that very quiet competence that has made the Passat one of the best-selling cars of all time. Earlier this week, the 30 millionth Passat rolled off the assembly line in Wolfsburg, Germany. That makes it the most successful mid-size car of all time, the second-best-selling Volkswagen of all time and one of the top five best-selling cars of any sort of all time.

The very first Passat was built in 1973 and marked the start of a revolution for Volkswagen. The German marque’s range up until then had consisted entirely of rear-engined, air-cooled models largely based on the Beetle. The Passat was a literal 180-degree turn, with a water-cooled engine at the front driving the front wheels.

VW’s previously curvaceous styling was banished too. Genius stylist Giorgetto Giugiaro penned a stylishly straight-edged, two-box hatchback body for the Passat which was itself a radical departure, as the Passat was competing in a class of three-box saloons like the Ford Cortina. Only Renault had previously taken the hatchback route, launching the 16 in 1965.

Estate and saloon bodystyles would be added to the range in due course, along with diesel engines. Subsequent generations gained four-wheel-drive and V6 engine options, too. The Passat has been sold under several other names around the world, including Dasher and Quantum. And in the last decade, VW introduced a Passat-badged car specifically tailored to the American market that actually shares very little with the car sold throughout the rest of the world.

In Europe, at least, the Passat is now into its eighth generation, known as B8, launched in 2014 and based on VW’s modular MQB platform. The 30 millionth Passat, a plug-in hybrid GTE estate, is actually a pre-production tester for the heavily updated B8 facelift, which is due on sale later this year.