BMW G20 330i vs M340i: Which Should You Buy?
The G20's central question. The 330i is the efficient, agile, sensible four; the M340i is the fast, smooth straight-six with the performance hardware to back it up. Both share the same excellent chassis and cabin — so the real choice is how much pace, sound and budget you want.
Good to know. Specs below are approximate and vary by market, model year and drivetrain — always confirm for the exact car. For reliability by engine, pair this with our G20 reliability guide.
Both cars are turbocharged, rear-biased and built on BMW's modular engines, so neither carries an engine you need to fear. What separates them is character and capability: the B48 four in the 330i is light, frugal and quick enough; the B58 six in the M340i is in another league for pace, and brings adaptive suspension, a limited-slip differential and bigger brakes as standard fare.
Head to Head
The numbers at a glance — approximate, by market.
Which Should You Buy?
Buy the 330i if…
- You want a premium daily that's quick enough and rewarding without the running costs of a six.
- Economy and insurance matter — the four is cheaper to fuel, insure and tyre.
- You like the lighter front end and the agility that comes with less weight over the nose.
- You'd rather spend the saving on options, a tune, or simply keep it in your pocket.
Buy the M340i if…
- You want serious pace and the smooth straight-six character and sound a four can't match.
- You value the hardware — adaptive M suspension, a limited-slip diff and bigger brakes as standard.
- You might tune it — the B58 has huge headroom and a deep aftermarket.
- The higher fuel, insurance and purchase cost is worth it for a near-M experience.
Not the full M3
The M340i is the performance flagship of the regular range, not the full M car — that's the separate G80 M3, with the twin-turbo S58, a stiffer setup and a higher price. The M340i is the sweet spot for most: most of the thrill, none of the hardcore compromises.
What They Share
Whichever you pick, you get the same core car: a superb chassis, a high-quality tech-rich cabin, the same iDrive and driver aids, and dependable modular engines (full breakdown in the reliability guide). Servicing is similar too — start with the oil change, and kit either one out with our G20 accessories picks.
FAQ
Is the M340i worth the extra over a 330i?
If you value performance and the straight-six, yes — it's dramatically faster and comes with adaptive suspension, an LSD and bigger brakes built in, for a near-M experience. If you mainly want a refined daily, the 330i delivers most of the joy for less to buy and run.
Is the 330i fast enough?
For most people, easily — around 5.6 seconds to 60 is genuinely quick, and the lighter nose makes it feel agile. It only feels "slow" next to the M340i; on its own it's a brisk, satisfying car, and it tunes up nicely if you want more.
xDrive or rear-wheel drive?
xDrive adds all-weather traction and quicker launches (the M340i is xDrive in many markets); rear-wheel drive is lighter and purer to drive. Choose by your climate and taste — both are excellent in the G20.
Which is cheaper to own?
The 330i, clearly — the four uses less fuel, costs less to insure and is easier on tyres and brakes. The M340i's performance hardware and bigger six cost more across the board, though both are reliable modular engines.
Can you tune a 330i?
Yes — the B48 responds well to a tune and bolt-ons for a meaningful bump. The B58 in the M340i simply has far more headroom, so a tuned 330i closes some of the gap but doesn't overtake a tuned M340i.
The Verdict
There's no wrong answer — both are excellent. Pick the 330i for the sensible sweet spot: quick, efficient, agile and cheaper to live with. Pick the M340i if you want the straight-six pace, sound and hardware and the tuning potential, and the running costs don't put you off. Decide on engine character and budget, then sanity-check the car against our reliability guide and head back to the G20 hub.