BMW M340i vs M3: is the full M car worth the extra?
The M340i and M3 share a body but offer very different experiences. Engines, performance, comfort, running costs, practicality and whether the full M3 is worth the extra money.
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M340i vs M3 is one of the most common questions for buyers of a fast BMW 3 Series. Both are four-door saloons, both are very fast, and the M340i costs much less to buy and run.
The M340i is an M Performance model: a regular 3 Series tuned by BMW M for more speed and agility. The M3 is a full M car with its own engine, chassis and character. In this comparison we look at the engines, performance, driving feel, comfort, costs and practicality to help you decide which one is right for you.
Two levels of performance
BMW offers fast versions of its cars at two levels. M Performance models, such as the M340i, sit between the regular models and the full M cars. They have stronger engines, sportier suspension and M design details, but they are built on the same base as the normal 3 Series.
Full M cars, such as the M3, are developed by BMW M with dedicated engines, wider bodies, stiffer structures and track-capable systems. Our article on BMW M vs M Performance vs M Sport explains the three levels in more detail.
M340i vs M3: engines
The engine is the biggest difference in the M340i vs M3 comparison:
- M340i: the B58 3.0-litre straight-six with a single twin-scroll turbocharger, producing around 374 hp in many markets. It is smooth, strong at low revs and efficient. Mild hybrid technology was added in some markets.
- M3: the S58 3.0-litre twin-turbo straight-six, developed by BMW M, with 480 hp in the standard car and 510 hp or more in the Competition. It revs harder and is built for sustained track use.
Both engines are excellent. The M340i feels effortless in everyday driving, while the M3 feels more urgent and dramatic. Our article on the BMW S58 engine explains the M3 engine.
Performance
The M340i is already very fast. With xDrive, it accelerates from 0 to 100 km/h in around four and a half seconds, which is enough to surprise many sports cars.
The M3 is faster still, especially in the Competition with xDrive, and it keeps its pace lap after lap on a circuit thanks to stronger brakes, better cooling and a more sophisticated chassis.
On public roads, the difference in real usable speed is smaller than the numbers suggest. The M3's advantages become clear on a track or on demanding roads driven at a high pace.
Gearboxes and drive
The M340i uses an eight-speed automatic gearbox and is available with rear-wheel drive or xDrive, depending on the market. An electronically controlled M Sport differential improves traction on many cars.
The M3 offers a six-speed manual in the standard version in many markets, and an eight-speed M Steptronic in the Competition. M xDrive includes a rear-wheel drive mode for experienced drivers on a circuit. Our article on M xDrive explains how it works.
Driving feel and comfort
The M340i is comfortable, quiet and easy to drive every day. Its suspension is firmer than a regular 3 Series, but it handles bumpy roads well. It is an excellent car for long journeys.
The M3 is firmer, louder and more focused. It has wider tracks, stiffer mounts and more precise steering. With adaptive suspension in its softer setting, it is comfortable enough for daily use, but you always feel that it is a sports car.
If most of your driving is commuting and motorway travel, the M340i may actually be the more enjoyable car.
Running costs
Running costs are a major difference:
- Fuel: the M340i usually uses noticeably less fuel.
- Tyres and brakes: the M3 uses wider tyres and larger brakes, which cost more to replace.
- Insurance: usually higher for the M3.
- Servicing: M engines need specific oils and more careful maintenance.
Our guide to BMW M car running costs gives a realistic picture of what owning a full M car involves.
Practicality
Both cars are four-door saloons with similar space for passengers and luggage. The M340i is also available as a Touring in many markets, and the M3 is available as the M3 Touring.
The M340i has a lower ride height and a less aggressive front bumper than the M3, which can be an advantage on steep driveways and speed bumps.
Which should you choose?
Choose the M340i if:
- you want a fast, comfortable daily car with lower running costs;
- you rarely drive on track;
- you value a quieter, more relaxed character.
Choose the M3 if:
- you want the full M experience, sound and character;
- you plan to drive on track or on demanding roads often;
- you prefer a manual gearbox or the most powerful options.
Test drive both. Many buyers who plan to buy an M3 discover that the M340i suits their daily life better, and many M3 owners say they would never go back.
M340i vs M3 at a glance
| Item | Details |
|---|---|
| Category | M340i: M Performance | M3: full M car |
| Engine | M340i: B58 3.0 | M3: S58 3.0 twin-turbo |
| Power | M340i: around 374 hp | M3: 480–510 hp and more |
| Gearbox | M340i: 8-speed auto | M3: manual or 8-speed M Steptronic |
| Drive | M340i: RWD or xDrive | M3: RWD or M xDrive |
| Character | M340i: comfortable, fast | M3: sharp, track-capable |
| Running costs | M340i noticeably lower |
Frequently asked questions
Is the M340i as fast as the M3?
No. The M340i is very fast, but the M3 has much more power and a chassis built for track use.
Is the M340i a real M car?
It is an M Performance model, tuned by BMW M, but not a full M car like the M3.
Is the M3 worth the extra money over the M340i?
If you want the full M experience and plan to use the performance, yes. For daily driving, the M340i is often the more sensible choice.
Is the M340i cheaper to run than the M3?
Yes. Fuel, tyres, brakes and insurance are usually noticeably cheaper.
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