The BMW E12 is the first generation of 5 Series executive cars, which was produced from 1972 to 1981 and replaced the saloon models of the BMW New Class range.

Initial models were powered by inline-four engines, using either a carburettor or fuel-injection. A year after launch, the first model powered by a straight-six engine was introduced. By the final years of E12 production, most models used a straight-six engine.

There was no M5 model for the E12, however the E12 M535i is considered to be the predecessor to the M5. The E24 6 Series coupés were built on the E12 platform up until 1982. The E12 was replaced by the E28 5 Series in 1981, although the tools were sent to South Africa where E12 assembly continued (with E28 interiors) until 1984.

The 518, 520 and 520i models were fitted with the 1.8 L and 2.0 L M10 inline-four engines, as per the previous New Class saloons. The 525, 528, 530, 530i and 533i models were fitted with M30 straight-six engines, as used in the New Six large saloons and E9 coupés. The 520, and 523 (the latter was developed, but never put into series production), use the M20 straight-six engine.

The 518 had its fuel supplied by a Solex 32/32 DIDTA carburetor, while the initial 520 model (powered by the M10 inline-four engine) used twin Stromberg 175CDET carburettors. The straight-six engine 525 and 528 models used dual Zenith INAT two-barrel carburettors up until the 1976 facelift. The straight-six 520 used a Solex 4A1 carburettor.

Fuel-injected models have the letter i at the end of their model designation. The 520i used the Kugelfischer mechanical fuel injection system from the 2000tii and 2002tii until 1975. From 1975, it was fitted with a mechanical continuous Bosch K-Jetronic port injection. The 518i (only sold in Sweden and Japan), 528i, and 530i (only sold in the US and Japan) have a Bosch L-Jetronic port injection.

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