BMW N55B30 engine code explained
N55B30 is the full code for BMW's single twin-scroll-turbo straight-six petrol of 2009 to 2018, the engine that replaced the N54 in the 135i, 335i, 535i, 640i, 740i, X3 35i, X5 35i and X6 35i, then powered the M135i, M235i, X4 M40i and the F87 M2 in higher-output form. Its Valvetronic head and single turbo made it far less troublesome than the N54, and the B58B30 that replaced it improved on it again.
Quick answer
The N55B30 is the 3.0-litre straight-six single twin-scroll turbo petrol of the BMW N55 family, built 2009-2018. Bimmer.AI scores the family 7 / 10: a strong used buy with a short list of known preventatives. The tables below give every output tier and sticker letter BMW used on this stem and which cars got them; the failure table is the same one that powers the N55 family guide.
How to read N55B30
| Part of the code | Meaning |
|---|---|
| N | N-series engine generation (2001 to about 2015) |
| 55 | engine family number within the N-series |
| B | petrol, longitudinal (rear-drive platform: 1 to 8 Series, X3 to X7, Z4) |
| 30 | displacement in tenths of a litre: 3.0 litres |
| K / U / M / O / T / S + digit | output tier and revision, appended in BMW's internal naming (for example N55B30O1) |
| A / B / C / D | parts-catalogue engine version printed on the engine cover sticker (for example N55B30A) |
N55B30 output tiers and which cars have them
| Code | Output | Cars | Notes |
|---|---|---|---|
| N55B30M0 | 302 to 306 bhp | 135i (E82 / E88 2010-2013), 335i (E90 / E92 / E93 2010-2013, F30 / F34 2012-2015), 435i (F32 / F33 / F36), 535i (F10 / F11 2010-2016), 640i (F06 / F12 / F13), 740i (F01 / F02), X1 xDrive35i (E84), X3 xDrive35i (F25), X4 xDrive35i (F26), X5 xDrive35i (E70 LCI, F15), X6 xDrive35i (E71, F16) | The volume tier |
| N55B30T0 | 316 to 365 bhp | M135i (F20 / F21 2012-2016, 316 then 322 bhp), M235i (F22 / F23, 322 bhp), X4 M40i (F26, 355 bhp), M2 (F87 2016-2018, 365 bhp) | M Performance tier; the M2 version has M-specific internals |
N55B30 sticker letters: N55B30A, N55B30B
The N55's letters mostly track output tier rather than a mechanical revision. Buyer checks are the same across all of them: wastegate rattle on the single turbo, the plastic charge pipe, the oil-filter-housing gasket, VANOS solenoids, the electric water pump and intake carbon build-up from the direct injection.
| Sticker code | What it denotes |
|---|---|
| N55B30A | Standard parts-catalogue version for the 302 to 306 bhp cars. |
| N55B30B | Later and M Performance applications (M135i, M235i, X4 M40i); the M2 unit is listed separately. |
Known problems on every N55B30
Failure data is held once, per engine family, so this table is identical to the BMW N55 guide. Cost ranges are indicative UK figures.
| Failure mode | Severity | Frequency | Typical onset | UK repair range |
|---|---|---|---|---|
| Wastegate actuator rattle | Mild | Very common | 40 to 100k mi | £200 to £800 |
| Plastic charge pipe failure | Moderate | Uncommon | 50 to 120k mi | £120 to £350 |
| VANOS solenoid weep or failure | Mild | Common | 60 to 130k mi | £150 to £400 |
| Oil filter housing gasket leak | Moderate | Common | 70 to 130k mi | £220 to £480 |
| Intake valve carbon buildup | Moderate | Common | 80 to 130k mi | £350 to £600 |
| Electric water pump failure | Moderate | Common | 70 to 130k mi | £500 to £750 |
Long-term verdict
Calmer reliability than the N54 it replaced. Wastegate rattle is the most-discussed quirk (mostly cosmetic). Plastic charge pipe is a known weak point worth upgrading past 100,000 miles. With documented servicing and the typical N5x preventative schedule, 200,000+ miles is realistic. Widely considered one of BMW's best modern petrols for value retention.
Check a specific N55B30 listing
Paste any BMW N55 listing, VIN or registration. Bimmer.AI identifies the exact engine and returns the buyer report in 30 seconds.
Run a Bimmer.AI buyer report →Bimmer.AI is designed to help you identify BMW-specific buyer risks before you travel, negotiate, or pay for an inspection. It does not replace a physical inspection by a qualified mechanic, a legal vehicle-history check (e.g. HPI Check), or independent verification of finance, stolen, or write-off status. Repair-cost ranges are indicative UK figures that vary by region, specialist, parts supply, and labour rates.
Frequently asked questions
N55B30 vs N54B30: which is more reliable?
The N55. It swapped the N54's twin turbos and piezo injectors for one twin-scroll turbo, Valvetronic and conventional solenoid injectors, which removed the two biggest N54 failure modes (HPFP and injectors) almost entirely. What is left is wastegate rattle, the charge pipe, the oil-filter-housing gasket and the water pump, all cheaper and more predictable. The N54 remains the tuner's engine; the N55 is the owner's engine.
Which BMWs have the N55B30T0?
The M Performance cars: M135i (F20 / F21, 2012 to 2016), M235i (F22 / F23), X4 M40i (F26) and the original F87 M2 (2016 to 2018). The M2 version has M3-derived pistons, a strengthened crank and an extra oil cooler, which is why BMW lists it separately in the parts catalogue. All are the same basic engine as the 306 bhp M0 with more boost and, on the M2, stronger internals.
Which BMWs have the N55B30 engine?
The N55B30 went into the following cars, by output tier. N55B30M0 (302 to 306 bhp): 135i (E82 / E88 2010-2013), 335i (E90 / E92 / E93 2010-2013, F30 / F34 2012-2015), 435i (F32 / F33 / F36), 535i (F10 / F11 2010-2016), 640i (F06 / F12 / F13), 740i (F01 / F02), X1 xDrive35i (E84), X3 xDrive35i (F25), X4 xDrive35i (F26), X5 xDrive35i (E70 LCI, F15), X6 xDrive35i (E71, F16); N55B30T0 (316 to 365 bhp): M135i (F20 / F21 2012-2016, 316 then 322 bhp), M235i (F22 / F23, 322 bhp), X4 M40i (F26, 355 bhp), M2 (F87 2016-2018, 365 bhp). The two-letter family badge is N55; any listing that quotes the family code is talking about one of these.
Is the BMW N55B30 reliable?
Bimmer.AI scores the N55 family 7 out of 10, which makes the N55B30 a strong used buy with a short list of known preventatives. Calmer reliability than the N54 it replaced. Wastegate rattle is the most-discussed quirk (mostly cosmetic). Plastic charge pipe is a known weak point worth upgrading past 100,000 miles. With documented servicing and the typical N5x preventative schedule, 200,000+ miles is realistic. Widely considered one of BMW's best modern petrols for value retention.
What does N55B30 mean?
N is the N-series engine generation (2001 to about 2015), 55 is the family number, B means petrol, longitudinal (rear-drive platform: 1 to 8 Series, X3 to X7, Z4), and 30 is the displacement in tenths of a litre (3.0 litres). BMW appends an output tier and revision (K, U, M, O, T or S plus a digit) in its own naming, and the parts catalogue adds a version letter (A, B, C) that is what you see on the engine cover.