BMW M30

The M30 is the engine BMW built for twenty-six years. Introduced in 1968 and made until
1994, this single-overhead-cam inline-six — the “Big Six” — powered the large
saloons and coupes that established BMW above the 2002: the E3 2500 and 2800, the E9 coupes,
every 6 Series, and the first two generations of 7 Series.

What the M30 is

A cast-iron-block inline-six with an aluminium cylinder head and a single overhead camshaft
driven by chain, made in displacements from 2.5 to 3.5 litres. The
1985 L7 brochure in this archive describes the
version in that car: a six-cylinder in-line engine, “longitudinally mounted and inclined”,
with a “light alloy cylinder head”, a crankshaft “with 7 main bearings and 12 counterweights”,
“pressure oil circulation, full-flow oil filter”, “Bosch L-Jetronic fuel injection, 3-way
catalyst with Lambda sensor, Digital Motor Electronics (Motronic)” and a capacity of 209 cubic
inches.

Two things in that list are worth pausing on. Seven main bearings for six cylinders means a
bearing between every throw — the arrangement that gives an inline-six its smoothness and
the reason BMW has kept building them. And the reference to Digital Motor Electronics dates
the car precisely: the same brochure notes BMW introduced “the first computer-controlled
engine” in 1979, and by 1985 it had reached the production saloons.

Where it appears in our records

Twenty-one specification pages, and they cover only the last five
years of an engine that ran for twenty-six. That is a limit of the source, not of the engine:
United States fuel economy records begin in the mid-1980s and detailed certification data much
later, so the 2500, the 3.0 CS, the 530i and the first-generation 733i are outside what we can
document from government filings.

Power figures are absent for the same reason — the certification records that carry
rated horsepower start in 1998, five years after the M30 finished. Combined fuel economy, which
the EPA did record, runs from 15 to 17 mpg.

Why it lasted twenty-six years

The M30 outlived four generations of the cars it went into. It began in the New Class-derived
saloons of the late 1960s and finished in the E34 535i, by which time BMW had introduced the
twin-cam M50 alongside it and the M30 was the large-displacement
option rather than the mainstream engine.

Its descendants are easy to trace. The M88 that powered the M1 is a four-valve,
twin-cam head on M30 architecture; the S38 of the E28 and E34 M5
comes from the same line. The M30 is the common ancestor of BMW’s performance sixes of the
1980s.

What we do not publish

No reliability rating. The NHTSA complaint database records faults against a
vehicle, not an engine, and for cars of this age the record is thin and skewed toward
whatever was still being complained about decades later. We also publish no power figures for
the M30, because no source we use carries them for these years.

Common questions

Which BMWs have the M30?

Over its life: the 2500, 2800, 3.0S and 3.0CS, the 530i, 528i, 533i and 535i, the 630CSi,
633CSi and 635CSi, and the 733i, 735i and 745i. In our United States specification records,
which begin in 1989, it appears in the 535i, 735i and 635CSi.

How much horsepower does the M30 have?

It depends entirely on displacement and year, and we do not publish a figure because the
government records we use do not carry one for any M30 year. What we can source is the
displacement in the 1985 L7 brochure: 209 cubic
inches, which is the 3.4-litre version.

Is the M30 the same as the M20?

No. Both are single-overhead-cam inline-sixes of the same era, and they are different
engines of different sizes: the M20 is the smaller “little six” of
the 3 Series and the 525i, the M30 the larger unit of the 5, 6 and 7 Series. They are not
interchangeable and share no major parts.

What replaced the M30?

The M60 V8 in the large cars and the twin-cam M50 six below it.
By 1995 the Big Six was out of production.

Sources

Quotations from the 1985 BMW L7 brochure in this
archive. Model years and fuel economy from EPA fuel economy data, with the source named on
every specification page.