BMW S38

The S38 is BMW M’s inline-six of the 1980s and early 1990s: a four-valve, twin-cam
development of the M30 Big Six, and the engine of the first two
M5s and the M6. It is the direct descendant of the M88 that powered the M1, and it is the
reason the E28 M5 exists at all.

What the S38 is

A 3.5-litre inline-six with two overhead camshafts, four valves per cylinder, six
individual throttle bodies and a cast-iron block inherited from the M30. Later versions grew
to 3.8 litres. It is an M division engine in the full sense: the S prefix means it was built by
BMW M GmbH, and as our guide to engine codes
explains, an S engine is a different unit rather than a tuned version of the road-car engine
with a similar number.

Its ancestry is unusually direct. The M88 was developed for the mid-engined M1 of 1978; the
S38 is that engine adapted for a front-engined saloon, with emissions equipment for markets
including the United States.

Where it appears in our records

Three specification pages, all E34 M5, at 13 to 14 mpg combined. The
E28 M5 of 1988 and the E24 M6 that shared the engine are outside our United States records:
detailed certification data does not reach back that far, and rated power appears in it only
from 1998, three years after the S38 finished.

Our brochure archive does not cover these cars either — the oldest M5 document we hold
is from 2006. Nothing on this page is quoted from a factory source, and where a figure would
require one, we leave it out.

How to tell a real one

These cars are old enough and valuable enough that badges get moved, and the engine is the
expensive part of the difference between an M5 and a 535i. The check that cannot be faked with
a parts order is in the VIN: a car built by BMW M GmbH carries WBS as its
first three characters rather than the WBA of an ordinary BMW AG car. That is the manufacturer
identifier, it is issued to the company that built the vehicle, and our
VIN decoder reads it straight out of the number without asking
anyone.

That check matters more for these cars than for modern ones. An M5 badge and a set of wheels
can be fitted to a 535i; the manufacturer identifier cannot.

What we do not publish

No reliability rating. The NHTSA complaint database records faults against a
vehicle, not an engine, and for a car built in the low thousands three decades ago the
complaint record is too thin to mean anything even in principle. We also publish no power,
torque or acceleration figures for the S38, because no source we hold carries them.

Common questions

Which BMWs have the S38?

The E28 M5, the E34 M5 and the E24 M6. In our United States specification records only the
E34 M5 of 1991 to 1993 appears.

How much horsepower does the S38 have?

We do not publish a figure. United States certification records carry rated power only from
1998, and we hold no period brochure for these cars. Numbers quoted elsewhere vary by market
and by displacement, and we are not going to repeat one we cannot trace.

Is the S38 the same as the M88?

They are the same design line. The M88 came first, in the M1 and the European M635CSi; the
S38 is the version developed from it for later cars and for markets with stricter emissions
rules.

How do I tell a real E34 M5?

Start with the VIN. Cars built by BMW M GmbH carry the WBS manufacturer identifier rather
than WBA, and that is not something a badge swap changes. Paste the number into the
decoder.

What replaced the S38?

The S62, a 4.9-litre V8, in the E39 M5 of 2000. The M5 has not
used a six-cylinder engine since: V8, then the S85 V10, then V8
again.

Sources

Model years and fuel economy from EPA fuel economy data, with the source named on every
specification page. Manufacturer identifier decoding from the VIN
structure itself, as described on our VIN decoder page. No brochure
from this period is held in the archive.