BMW M42

The M42 is BMW’s first twin-cam four-cylinder, built from 1989 to 1996. In the United States
it powered one car — the 318i and 318is — and it is the engine that brought
four-valve heads and engine management down from the M division into an ordinary 3 Series.

What the M42 is

A 1.8-litre inline-four with two overhead camshafts, four valves per cylinder and a
chain-driven timing arrangement. It replaced the single-cam M40 in
the sporting versions of the 3 Series, and it did to the four-cylinder range what the
M50 did to the sixes a year later: made the twin-cam,
four-valve layout ordinary.

We hold no United States brochure from these years — the 1990s are the decade missing
entirely from our archive — and certification records carrying rated power begin in 1998,
two years after the M42 finished. So this page publishes no horsepower figure. What EPA fuel
economy data gives, and gives precisely, is which cars had it.

Where it appears in our records

Six specification pages, every one of them 1,800 cc. That figure is the
whole trick of this page, because it is what separates the M42 from the engine that replaced
it.

1.8 or 1.9: how to tell an M42 from an M44

Both engines went into a car badged 318i, and the badge did not change when the engine did.
The displacement did, and the EPA recorded it:

A US 318i of 1995 or earlier is an M42; a 318i, 318ti or Z3 1.9 from 1996 onwards is an M44.
There is no overlap year in our records, which makes this one of the cleaner engine
identifications in BMW’s range — and it comes out of a government dataset rather than out
of a forum thread.

Where it sits in the range

The M42 was the sporting four, not the base one. Below it in Europe sat the single-cam
M40, which the United States never received; above it the
six-cylinder M50. That places the American 318is in an unusual
position: the entry-level 3 Series here was the one Europe treated as the sporting version.

The 318ti of 1995 is worth a note of its own. It is a three-door hatchback 3 Series, sold in
the United States for a few years and rare now, and it carries the same engine.

What we do not publish

No reliability rating. The NHTSA complaint database records faults against a
vehicle, not an engine, and a 1994 3 Series in that database may be a four-cylinder
318i or a six-cylinder 325i without the record saying which. The timing-chain and cooling-system
questions these engines are discussed for are maintenance history rather than measured failure
rates, and we do not publish rates we cannot trace.

Common questions

Which BMWs have the M42?

In the United States: the 318i, 318is and 318i Convertible of 1991 to 1995, and the 318ti of
1995. Elsewhere it also appeared in the E36 318is and the Z3 1.8.

How much horsepower does the M42 have?

We do not publish a figure. Certification records carrying rated power begin in 1998 and our
archive holds no brochure of the period. Displacement is 1,800 cc in every US application.

Is my 318i an M42 or an M44?

By model year: 1995 and earlier is an M42, 1996 and later is an
M44. The displacement confirms it — 1.8 against 1.9 litres
— and both figures are on the specification page for the year.

What is the difference between the M42 and the M40?

Camshafts and valves. The M40 is a single-cam eight-valve engine;
the M42 has two camshafts and sixteen valves. The M40 was never sold in the United States.

What replaced the M42?

The M44, from the 1996 model year, enlarged to 1.9 litres.

Sources

Cylinder counts, displacements, model years and fuel economy from EPA fuel economy data, with
the source named on every specification page. No brochure from this period
is held in the archive; the submission page explains what to
send.