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BMW B58

3.0 L · inline-6 · turbocharged · petrol · 2015–present

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Also known as: b58b30, 340i engine, m240i engine, 3.0 turbo straight-six, b58b30c, b58b30o1, b58b30m1

The straight-six of BMW's modular family, where every engine is built from a common 500 cc cylinder — which is why the B38 three, B48 four and B58 six share architecture, tooling and a great deal of diagnostic behaviour. An unfamiliar B-series fault is often documented under a sibling with a different cylinder count.

A single twin-scroll turbocharger replaces the N54's pair, and the closed-deck block, integrated exhaust manifold and indirect charge cooling between them removed most of what made the earlier turbo sixes fragile. It is the well-regarded member of the family, so the useful diagnostic posture is different: with far fewer characteristic failures, a fault on a B58 is more likely to be a genuine one-off than a known pattern, and pattern-matching from N54 experience will send you the wrong way.

Where it does complain, cooling-system plastics and the charge-air path are the places to start.

Cars fitted with this engine

18 generations, across 2 makes. From the authored catalogue — an absent car means the catalogue has not reached it, not that the engine was never fitted.

Information, not instruction

CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.

Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.

Posted about this engine

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What makes one worth reading:

  • The car — make, model, year and engine. The same fault behaves differently on each.
  • What you measured, not only what you replaced.
  • What actually fixed it — or that nothing did, which is worth knowing too.

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