BMW 335i vs 340i: N55 or B58 Straight-Six 3 Series?
335i vs 340i is the enthusiast six-cylinder 3 Series decision, and it turns almost entirely on one thing: the N55 to B58 engine step change. The 335i (F30 pre-LCI, 2012 to 2015) uses the single-turbo N55 that replaced the legendary N54. The 340i (F30 LCI, 2015 to 2019) uses the B58, one of BMW's best modern engines and the same unit that powers the Toyota Supra. This guide covers what actually changes between them for UK ownership.
Quick verdict
340i if you can stretch to it: the B58 is a meaningful upgrade on the N55 for power, refinement, ULEZ certainty, and tuning headroom. 335i if value is the priority and you accept the pre-LCI ULEZ check. The 340i is uniformly Euro 6 ULEZ-compliant; the 335i needs its V5 emissions class verified (many pre-2015 cars are Euro 5). Both share the standard N-series and B-series service pattern: charge pipe upgrade, water pump, VANOS solenoid, walnut blast for carbon buildup.
Side-by-side comparison
| Dimension | 335i | 340i | Notes |
|---|---|---|---|
| Engine | N55 3.0L single twin-scroll turbo, open-deck block | B58 3.0L single twin-scroll turbo, closed-deck block | B58 closed-deck block is stronger and handles more boost. |
| Power / torque (standard) | 306 bhp / 400 Nm | 322 bhp / 450 Nm | B58 adds power and a useful torque bump. |
| 0-62 mph (auto) | Around 5.4 seconds | Around 5.1 seconds | Both rapid; B58 is the quicker and more effortless of the two. |
| Production years (F30) | 2012 to 2015 (pre-LCI) | 2015 to 2019 (LCI) | The 340i replaced the 335i at the mid-2015 facelift. |
| Tuning headroom (stage 1 map) | +60 to +90 bhp | +80 to +120 bhp | B58 is one of the most tunable modern BMW engines; huge aftermarket. |
| ULEZ compliance | Verify on V5 (many pre-2015 are Euro 5) | Yes (Euro 6 from launch) | Single biggest London-buyer factor between the two. |
| Real-world UK MPG | 30 to 36 mpg combined | 34 to 40 mpg combined | B58 is modestly more efficient despite more power. |
| Refinement / NVH | Smooth six with slight wastegate rattle on some cars | Smoother still; quieter, more polished | B58 is the more refined unit; N55 wastegate rattle is a known cosmetic quirk. |
335i: deeper look
<p>The 335i (F30 pre-LCI, 2012 to 2015) uses the N55 single-turbo 3.0-litre straight-six: 306 bhp, 400 Nm, and 0-62 in around 5.4 seconds with the ZF 8-speed auto (a 6-speed manual was also offered). It is the calmer, single-turbo successor to the twin-turbo N54, with a simpler service story and no HPFP recall.</p><p>Buying an F30 335i in 2026 is a value play: clean cars sit well below 340i money, and the N55 is a well-understood engine with deep UK parts supply. The two watch-items are ULEZ compliance (verify the Euro class on the V5, as many 2012 to 2014 cars are Euro 5 and non-compliant) and the standard N55 service pattern: aluminium charge pipe upgrade, electric water pump, VANOS solenoids, oil filter housing gasket, and walnut blasting for intake carbon at around 60,000 to 80,000 miles.</p>
340i: deeper look
<p>The 340i (F30 LCI, 2015 to 2019) introduced the B58, the engine that changes this comparison. Closed-deck block, integrated exhaust manifold, improved cooling, and stronger internals give 322 bhp and 450 Nm as standard, plus a reputation as one of BMW's best modern petrol engines. It is the same fundamental unit used in the Toyota GR Supra, and the tuning community treats it as near-bulletproof at stage 1.</p><p>Beyond the engine, the LCI 340i brings Euro 6 emissions (ULEZ-compliant across the board), iDrive 6 NBT with Apple CarPlay availability, and LED lighting options. It still shares the modular service items (charge pipe, water pump, VANOS, walnut blast), but carries no pre-2015 timing-chain conversation and is the cleaner used buy on almost every axis except purchase price.</p>
Decision logic
Budget is the first filter. If you can reach 340i money (roughly £16,000 to £23,000 for a clean F30 LCI in 2026), the B58 is worth it: more power, more refinement, ULEZ certainty, and the strongest tuning platform of the two. If the budget caps out around £10,000 to £15,000, the 335i is the value six-cylinder pick, provided you verify the V5 emissions class for ULEZ and confirm the charge pipe has been upgraded. For a London-based buyer, the 340i removes the ULEZ question entirely and is the safer choice. For a tuner, both respond well, but the B58 has more safe headroom on stock hardware.
UK 2026 pricing comparison
| Scenario | 335i | 340i | Notes |
|---|---|---|---|
| F30 335i M Sport, 80k miles (N55) | £10,000 to £14,000 | £16,000 to £20,000 (340i M Sport LCI equivalent) | 340i commands a clear premium for the B58 and ULEZ compliance. |
| F30 340i M Sport, 60k miles (B58) | £12,000 to £15,000 (335i equivalent, higher miles) | £18,000 to £23,000 | Freshest LCI 340i cars; strongest six-cylinder F30 residuals. |
| xDrive M Sport, 70k miles | £11,000 to £15,000 (335i xDrive) | £19,000 to £24,000 (340i xDrive) | xDrive adds around £1,000 to £2,000 over RWD on both. |
| Manual gearbox example | £11,000 to £15,500 (335i manual, uncommon) | £18,000 to £24,000 (340i manual, sought-after) | Manual 340i is an enthusiast favourite and holds value well. |
| Lightly tuned stage 1 example | £10,000 to £14,000 (335i, verify tune quality) | £17,000 to £23,000 (340i, verify tune quality) | Documented reputable tunes are fine; unknown maps are buyer leverage. |
Recommendation by scenario
| Scenario | Pick | Why |
|---|---|---|
| London commuter inside ULEZ | 340i (B58) | Euro 6 ULEZ-compliant from launch; no V5 emissions gamble. The 335i needs its emissions class verified and many pre-2015 cars are Euro 5. |
| Tuning enthusiast | 340i (B58) | The B58 is one of the most tunable modern BMW engines with large safe stage 1 headroom on stock hardware and a deep aftermarket. The N55 tunes well but the B58 is the stronger platform. |
| Value six-cylinder buyer (sub-£15,000) | 335i M Sport (N55) with charge pipe done | Cheapest route into a modern straight-six F30. Verify V5 emissions class and confirm the aluminium charge pipe upgrade; budget walnut blasting if overdue. |
| Everyday fast saloon | 340i M Sport auto | Effortless torque, refined B58, ZF 8-speed. The best all-round six-cylinder F30 for daily use if budget allows. |
| Manual-gearbox seeker | 340i manual if you can find one, else 335i manual | Both offered a 6-speed manual. The manual 340i is sought-after and holds value; the manual 335i is the cheaper way into a three-pedal straight-six 3 Series. |
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Frequently asked questions
Is the B58 340i really a big step up from the N55 335i?
Yes, meaningfully. The B58 adds power (322 bhp vs 306 bhp) and torque (450 Nm vs 400 Nm), but the bigger gains are in the closed-deck block strength, improved cooling, refinement, and tuning headroom. The B58 is widely regarded as one of BMW's best modern engines and is the same fundamental unit used in the Toyota GR Supra. The N55 is still a good engine, but the B58 is the clear technical upgrade.
Is the 335i ULEZ-compliant?
It depends on the individual car. Many F30 335i cars from 2012 to 2014 are Euro 5 and NOT ULEZ-compliant; some later pre-LCI cars are Euro 6. You must verify the emissions class on the V5 before purchase. The 340i (F30 LCI, 2015 to 2019) is Euro 6 and ULEZ-compliant across the board, which is a key reason London buyers gravitate to it.
How much more is a 340i than a 335i in 2026?
Roughly £5,000 to £8,000 more for comparable age and mileage. A clean F30 335i M Sport at 80,000 miles is around £10,000 to £14,000; a comparable 340i M Sport is around £16,000 to £23,000. The premium buys the B58, Euro 6 ULEZ compliance, iDrive 6 NBT with CarPlay availability, and stronger residual values.
Which tunes better, N55 or B58?
Both respond well to a stage 1 map, but the B58 has more safe headroom. N55 stage 1 typically adds 60 to 90 bhp; B58 stage 1 typically adds 80 to 120 bhp, and the closed-deck block plus stronger internals give it a higher ceiling for stage 2 and beyond. The B58 aftermarket is one of the deepest of any modern BMW engine.
Do the 335i and 340i share the same service items?
Largely yes. Both use aluminium charge pipe upgrades (the OEM plastic pipe is a known weak point), electric water pumps, VANOS solenoids, oil filter housing gaskets, and periodic walnut blasting for intake-valve carbon (both are direct-injection engines). The N55 has the wastegate rattle as a cosmetic quirk; the B58 is generally quieter and more refined.
Is the 340i reliable enough to buy with high miles?
Yes, the B58 is regarded as a durable, well-engineered engine, and high-mileage examples with full service history are a reasonable buy. Prioritise cars with documented oil services, a fitted charge pipe upgrade, and evidence of walnut blasting if past 70,000 miles. As with any used BMW six, service history matters more than the odometer number alone.
Should I just buy an M340i (G20) instead?
If budget allows, the G20 M340i (B58 with more power, around 369 bhp, plus xDrive and iDrive 7/8) is the newer and quicker option, but it costs meaningfully more (roughly £30,000 to £38,000). The F30 340i is the value B58 pick. The 335i vs 340i decision is about staying within F30 money; the M340i is a separate, higher-budget conversation.