BMW B58 Gets a 392-HP Boost: Is the M340i the Sweet Spot?

You know that feeling when your favorite recipe gets a little extra kick, and suddenly it’s even more addictive? That’s exactly what happened in 2025 when BMW decided to spice up the B58 3.0-liter TwinPower Turbo straight-six in the M340i, M440i, and M240i. Even though we’re already well into 2026, I still can’t stop thinking about how this subtle power bump reshaped the M Performance lineup. Why? Because sometimes the best upgrades aren’t about massive horsepower wars—they’re about perfecting the balance between daily drivability and straight-up grin-inducing acceleration.

Let’s rewind to late 2025. BMW quietly dropped a mid-cycle update, and the M340i xDrive was the first to benefit. The sedan and the Touring wagon both woke up with 392 horsepower and 398 lb-ft of torque—that’s an extra 18 hp and 30 lb-ft compared to the pre-update models. Does 18 horsepower sound like pocket change? Maybe, if you compare it to a monster like the M3 Competition. But here’s a fun fact: that bump is literally the output of a standard walk-behind lawnmower. You’re now carrying a whole lawnmower’s worth of extra shove under the hood, but you’d never guess it from the polished cabin or the seamless way the eight-speed automatic delivers the goods. The 48-volt mild hybrid system still chips in with 12 hp, so the overall package feels more urgent than the numbers suggest.

So what does all this translate to on the road? The 0-60 mph sprint drops from 4.4 seconds to 4.3 seconds
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