BMW S63 / S68

The M division's 4.4 twin-turbo V8 — the S63, and the S68 that replaced it from 2022 with a 48-volt starter-generator — in the M5, M8, X5 M, X6 M, X7, XM, and, bought in, the Range Rover Sport SV. The standard-range engine of the same architecture is the N63.

The turbochargers sit inside the vee and that is the whole of its service character. Everything between the banks runs extremely hot and is very hard to reach, so coolant lines, wiring and sensors in that space age far faster than their equivalents on a naturally aspirated V8, and labour dominates any estimate. Heat is the mechanism behind most of what fails here, which is why an engine that has been tracked or tuned is a materially different proposition from one that has not.

Its cross-bank exhaust manifold is the identifying feature, pairing cylinders from opposite banks to even out the pulses reaching each turbocharger — and it is the reason exhaust work on this engine bears no resemblance to a conventional V8's.

Beyond the vee, the recurring items are oil consumption and the crankcase ventilation system, VANOS solenoids, and the timing chain at high mileage. Establish which revision is fitted before quoting anything: BMW revised this engine substantially more than once, and the S68's mild-hybrid integration adds a system the S63 does not have.