BMW M40

The M40 is BMW’s single-overhead-cam four-cylinder of the late 1980s, built from 1987 to
1994. It replaced the long-running M10 in the base 3 and 5 Series
— and it never came to the United States. This page exists because people search for it,
and because saying so plainly is more useful than a page that implies otherwise.

What the M40 is

A 1.6 and 1.8-litre inline-four with a single overhead camshaft driven by a toothed belt
rather than a chain, and two valves per cylinder. It was the economy engine of the E30 and E34
range: 316i, 318i and 518i in the European market.

Against the M42 that arrived alongside it, the M40 is the simpler
and cheaper of the two — single camshaft against twin, eight valves against sixteen, belt
against chain. BMW sold both at once, the M40 below and the M42 in the sporting versions.

Why it is not in our records

Our specification pages are built from United States government data: EPA fuel economy
records, EPA certification test results and Transport Canada vehicle specifications. A car not
sold in North America appears in none of them, and the M40 was not sold here.

The American 318i of those years is a different car with a different engine. Up to 1995 it
uses the twin-cam M42; from 1996 the
M44. Both are 1.8 and 1.9-litre sixteen-valve engines, and both are
in our records with model years and fuel economy. If you are in the United States and looking at
a 318i, it is one of those two.

Our brochure archive is a United States archive for the same reason, so it holds nothing that
describes the M40 either. Where we have no source, we publish no figures — that is the
rule for every page on this site and it applies here more completely than most.

What we can say, and where it comes from

The configuration above — displacements, camshaft arrangement, valve count, the models
it went into — is general engineering description rather than anything we can point at a
document for. We are flagging that rather than dressing it up: on pages where a figure carries a
source, this site names the source, and there is none to name here.

If you hold a European brochure or price list covering a 316i, 318i or 518i of this period,
the submission page explains what to send. A document would let
this page say something we can stand behind.

What we do not publish

No reliability rating, no power figures, and no specification table. The NHTSA complaint
database covers vehicles sold in the United States, and this engine was not one of them, so
there is not even a flawed dataset to misuse. The timing-belt interval these engines are
discussed for is a maintenance item in a service schedule rather than a failure statistic.

Common questions

Which BMWs have the M40?

The E30 316i and 318i and the E34 518i, in Europe and other markets, from 1987 to 1994. None
were sold new in the United States.

Did the American 318i have an M40?

No. United States 318i cars use the M42 from 1991 to 1995 and the
M44 from 1996 to 1998 — both twin-cam sixteen-valve engines,
both in our specification records.

What is the difference between the M40 and the M42?

The M40 has one camshaft and eight valves and drives its camshaft by belt; the M42 has two
camshafts, sixteen valves and a chain. They were sold alongside each other, the M40 in base
models and the M42 in sporting ones.

What replaced the M40?

The M43, from 1991 alongside it and fully from 1994. That engine was not sold in the United
States either.

Sources

None for this engine, and that is the point of the page. Nothing here comes from EPA
certification data, EPA fuel economy data, Transport Canada records or a brochure in this
archive, because none of them cover a car that was never sold in the United States. Every other
engine page on this site names its sources; this one has none to name.