What Every Owner and Used-Car Buyer Should Know The BMW 3 Series has earned its reputation as one of the best-driving executive cars in the world. Since its introduction in 1975, the model has combined rear-wheel-drive dynamics, strong engines, premium interiors and everyday practicality in a package that has attracted millions of drivers. But there is another side to owning a BMW 3 Series:  maintenance and repairs can become expensive when common problems are ignored . That does not mean every BMW 3 Series is unreliable. Far from it. A well-maintained 3 Series can provide years of enjoyable and dependable service. The important point is that different generations and engines have very different weak points. An E90 320d, an F30 328i, a 340i and a newer G20 330i may all carry the 3 Series badge, but their potential problems can be completely different. If you are thinking about buying a used BMW 3 Series, or you already own one, knowing what to look for can save you thousands...