BMW B58 Buying Guide: What to Look For

The B58 is BMW’s 3.0-litre single-turbo straight-six petrol engine, launched in 2015 to replace the N55. It’s become a bit of a modern legend — genuinely reliable, and one of the most tuneable engines BMW has ever built. If you’re shopping for one, here’s what you’re buying and what to check.

Which BMWs have the B58?

You’ll find it in the 140i, M140i, 240i, M240i, 340i, M340i, 440i, M440i, 540i and 740i, plus the X3 M40i, X4 M40i and Z4 M40i — and, famously, the Toyota GR Supra. In short: if it’s a modern six-cylinder petrol BMW that isn’t a full-fat M car, it’s almost certainly a B58.

B58 vs B58TÜ

There are two flavours. The original B58 (roughly 2015–2018) and the updated B58TÜ (from around 2019, in G-series cars like the M340i and the Supra). The TÜ gained a closed-deck block, revised cooling and added port injection alongside direct injection — making an already-strong engine even better and cleaner-running. Both tune brilliantly.

What to check when buying

• Service history. These make big power and big heat — you want to see regular oil changes with the correct spec, not stretched “lifetime” intervals.
• Cooling. The electric water pump and thermostat are wear items; ask when they were last done and watch for any overheating.
• Charge pipe. The plastic charge pipe can crack under boost — a cheap fix and a common upgrade, especially on tuned cars.
• Oil leaks. Valve-cover and oil-filter-housing gaskets can weep with age — minor, but worth spotting.
• Carbon build-up. Early direct-injection B58s can gather some inlet carbon over high miles (the TÜ’s port injection helps). Not a dealbreaker — just budget for a possible walnut-blast eventually.
• Has it been tuned? Many have, and that’s not a bad thing — but ask who did it, whether it was a proper custom map, and whether the original file was saved. A good tune adds value; a bad one hides sins.

Why it’s a tuner’s dream

This is the B58’s party trick. The bottom end is strong enough that a custom Stage 1 alone makes a big, safe jump in power and torque — and the engine happily takes far more with bolt-ons and higher-octane fuel. Almost all are paired with the ZF 8-speed auto, which loves an xHP gearbox tune to match the extra torque and sharpen the shifts (do both together and save £125).

As with everything we do, a B58 tune starts with a full health check — we only tune a healthy engine — and it’s fully reversible.

Bought one, or about to? Check your exact car for gains and pricing, read up on M140i / M240i tuning, then book a slot or get a quote.