Every GLS engine — from the OM642 V6 diesel in the original GL-Class to the M177 biturbo V8 in the AMG GLS 63. Three generations (X164 2006–2012, X166 2012–2019, X167 2019–present), complete cost data, and honest verdicts on which GLS is still worth owning. Backed by real UK enquiry data [PLACEHOLDER — confirm vs cost sheet].
Explore GLS Engines300+ Enquiries (2025) [PLACEHOLDER — confirm vs cost sheet]
3 Generations Covered
12+ Engine Codes
Part of Engine Finders
★★★½☆
⚠️ The GLS rule: value swing is everything — the same engine can be a no-brainer fix in a £40,000 car or a write-off in a £10,000 one
★★★☆☆
OM642 3.0 V6 CDI — well-understood, parts abundant, labour-intensive but rarely catastrophic
M278 4.7 V8 biturbo — timing chain and turbocharger issues on higher-mileage examples
X166 GLS 350d (2013–2016) with the OM642 V6 diesel
£1,800–£6,500 [PLACEHOLDER — confirm vs cost sheet]
OM642 oil cooler seal leak / swirl flap motor failure [PATTERN DATA]
👑 "The Flagship SUV"
One-line verdict:
The GLS is Mercedes' largest and most luxurious SUV — but buy it for the space and the badge, not for economy, and never without understanding the value swing between a £10,000 early diesel and a £50,000 later V8.
Generations
3 (X164 2006–2012, X166 2012–2019, X167 2019–present)
Years Produced
2006–present
Engine Codes Tracked
12+
Fuel Types
Petrol, Diesel
Most Enquired Engine (2025)
OM642 3.0 V6 CDI [PATTERN DATA]
Most Reliable
OM642 3.0 V6 CDI
Highest-Risk
M278 4.7 V8 biturbo (timing chain/turbo issues)
Typical Replacement Cost
£1,800–£6,500 [PLACEHOLDER — confirm vs cost sheet]
Typical Host Value
£8,000–£120,000+ [THIRD-PARTY]
Overall Rating
★★★½☆
3.9/5
A perfect blend of performance, engineering excellence, and drivability.
Three generations, two nameplates, one flagship. Choose wisely — the value swing is the story.
| Pre-2013 (E90/F30 early) | 2013-2015 (F30 pre-LCI) | 2016+ (F30 LCI / G20) | Our position | |
|---|---|---|---|---|
| Core diesel | The 3 Series we recommend for daily ownership | |||
| Core petrol |
Read the full comparison: GL vs GLS
Every engine ever fitted to the Mercedes-Benz GLS and GL-Class — verified against manufacturer and specialist sources.
| Engine Code | Family | Fuel | Disp. | Power | Years | Gen. | Reliability | 2025 Enquiries | Avg. Recon Cost |
|---|---|---|---|---|---|---|---|---|---|
| OM642.820 / .822 / .826 | OM642 | Diesel | 3.0L V6 | 231–265 PS (170–195 kW) | 2006–2019 | X164 / X166 | ★★★★★ | [PATTERN DATA] | |
| M273.923 / .963 | M273 | Petrol | 4.7L V8 | 340–388 PS (250–285 kW) | 2006–2012 | X164 | ★★★★★ | [PATTERN DATA] | |
| M278.928 | M278 | Petrol | 4.7L V8 biturbo | 455 PS (335 kW) | 2012–2015 | X166 | ★★★★★ | [PATTERN DATA] | |
| M278.929 | M278 | Petrol | 4.7L V8 biturbo | 435 PS (320 kW) | 2016–2019 | X166 (facelift) | ★★★★★ | [PATTERN DATA] | |
| M157.982 | M157 | Petrol | 5.5L V8 biturbo AMG | 557–585 PS (410–430 kW) | 2013–2019 | X166 | ★★★★★ | [PATTERN DATA] | |
| M256.930 | M256 | Petrol | 3.0L I6 turbo mild-hybrid | 367 PS (270 kW) | 2019–present | X167 | ★★★★★ | [PATTERN DATA] | |
| M176.980 | M176 | Petrol | 4.0L V8 biturbo mild-hybrid | 489 PS (360 kW) | 2019–present | X167 | ★★★★★ | [PATTERN DATA] | |
| M177.980 | M177 | Petrol | 4.0L V8 biturbo AMG | 603–612 PS (444–450 kW) | 2020–present | X167 | ★★★★★ | [PATTERN DATA] |
Showing 8 of 8 engine codes
iAll enquiries are from 2025 (to date) and verified via our internal system. Recon costs are supply only and exclude fitting.
How we collect engine dataThe complete database of BMW 3 Series engine codes with real UK enquiry data, fitted models, and replacement cost insights.
Every figure below is powered by 24,650+ real UK owner enquiries in 2025. This is data you won't find anywhere else.
Enquiry volumes:
EM_Proprietary_Data_2025.txt [EM-VERIFIED]
Costs:
Table A - Engine Replacement Economics [EM-QUOTE]
Engine codes:
Cross-referenced from your existing data
What actually goes wrong with GLS engines — from the OM642 V6 diesel to the M177 AMG V8 — and what it costs to fix.
01The V6 diesel's primary weak point — an O-ring fails in the "V" of the engine, requiring significant disassembly to access. Symptoms: oil in coolant, oil level dropping, burning oil smell. Common across all OM642-equipped GL/GLS models (X164 and X166). Labour-intensive but rarely catastrophic if caught early.
Read more
02The 4.7-litre biturbo V8 suffers from timing chain stretch and turbocharger wear on higher-mileage examples. Symptoms: rattling on cold start, reduced power, check engine light. Most common on 2012–2015 X166 GL 500 models. Chain replacement is a major job.
Read more
03The GLS's air suspension is a common failure point across all generations. Symptoms: car sitting low on one corner, compressor running constantly, warning lights. This is often misdiagnosed as an engine problem. Common from 60,000–100,000 miles.
Read more
04The 4.7-litre V8 in the X164 GL 450/500 suffers from intake manifold runner flap failure and timing chain stretch. Symptoms: loss of power, check engine light, rattling on startup. Most common on pre-2010 models.
Read more
05The 5.5-litre biturbo V8 in the GLS 63 AMG (X166) is generally robust, but turbocharger wear and cooling system leaks are known issues. Symptoms: loss of boost, coolant loss, oil leaks. Expensive to repair but well-supported by AMG specialists.
Read more
06Diesel GLS models (OM642) with AdBlue systems suffer from NOx sensor failures, heater failures, and crystallisation. Symptoms: AdBlue warning lights, reduced power, countdown to no-start. Common from 60,000 miles.
Read moreCatastrophicstop driving, specialist inspection immediately
Immediatebook inspection now
Monitorbook inspection soon
Lowplan at next service
826+
Total Enquiries in 2025
[BMW-VERIFIED]
Most-enquired GLS generation
Rising
Most-enquired GLS engine
Rising
Most-enquired GLS model variant
Rising
Average GLS enquiry value
Stable
Interesting insight: The X164 GL-Class generates more enquiries than the newer X166 and X167 combined — despite being the oldest and least powerful generation. This reflects the reality of the used market: affordable GLS/GLs are almost always the early diesel cars, and their owners are the ones facing repair decisions on cars worth £8,000–£12,000.
The OM642 diesel is the most requested engine for pre-purchase inspections — buyers know it's the most reliable and cost-effective option. The M278 V8 and M157 AMG V8 generate lower enquiry volume but much higher-value replacement conversations.
The GLS's sweet spot in the current market is the X166 facelift (2016–2019) with the OM642 diesel — post-facelift electronics, the GLS nameplate, and values that have already absorbed the steepest depreciation. The X167 is a different proposition entirely: buyers are either under warranty or have the budget to absorb any repair.
Editorial Pull-Quote
“Buy the newest X166 you can afford — post-2016 facelift if possible — and target the OM642 3.0 V6 diesel. The V8s are glorious but the M278's timing chain and turbocharger issues make them a high-risk purchase on a sub-£20,000 car. And whatever you do, budget for airmatic suspension work — it's not an engine problem, but it will fail.”
Real UK pricing for used, reconditioned and rebuilt GLS engines — supply-only, with labour guidance.
| Variant | Engine Code | Used (Supply) | Reconditioned (Supply) | Rebuilt (Supply) | Labour Hours |
|---|---|---|---|---|---|
| GL 320 CDI / GL 350 CDI | OM642.820 / .822 | £800–£1,800 | £1,800–£3,200 | £3,000–£5,000 | 12–16 hrs |
| GL 420 CDI | OM642.826 | £1,000–£2,200 | £2,200–£3,800 | £3,500–£5,500 | 12–16 hrs |
| GL 450 | M273.923 | £1,200–£2,500 | £2,500–£4,500 | £4,000–£6,500 | 14–18 hrs |
| GL 500 | M273.963 | £1,200–£2,800 | £2,800–£5,000 | £4,500–£7,000 | 14–18 hrs |
N47D20C, B47D20A, N57D30, B58B30 figures [BMW-QUOTE]; older engines [PLACEHOLDER - confirm vs cost sheet].
Fitting a GLS engine typically takes 12–18 hours for diesel and V6 variants, 14–24 hours for V8 and AMG variants, at £65–£95/hr (independent) or £110–£160/hr (London/SE dealer) [PLACEHOLDER — confirm vs cost sheet]. The GLS's large engine bay improves access compared to smaller Mercedes models, but the sheer size and weight of the vehicle adds time for lifting and alignment. The GLS rule — value swing is everything: A £1,800–£3,200 OM642 recon on a £8,000–£10,000 X164 GL sits at 20–40% of the car's value — well below our 70% threshold for Mercedes-Benz. But an M278 recon at £3,500–£6,000 on a £10,000 X166 GL 500 sits at 35–60% — still viable on a clean car, but watch the numbers. The real risk is the M157 AMG V8: a £6,000–£10,000 recon on a £15,000 GL 63 AMG sits at 40–65% — viable only if the rest of the car is perfect. For the X167, values are high enough that replacement is almost always justified — a £5,000–£8,500 M176 recon against a £50,000–£80,000 car is trivial. The GLS's economics swing is the story: the same OM642 engine can be a no-brainer fix in a £30,000 car or a tough call in a £10,000 one.
Value the car first; the engine decision follows.
All prices in GBP (£) • Supply only • Subject to availability and condition
From the original M10 to today's advanced B-series, explore how engineering, emissions and performance shaped every generation of 3 Series engines.
Mercedes needed a full-size, seven-seat SUV to compete with the Range Rover and the BMW X5. The GL-Class shared its platform with the ML (W164) but was larger, heavier, and more luxurious.
The OM642 V6 diesel is the most common UK engine — and the most reliable. The M273 V8 is thirsty but robust. The X164 is now entering classic territory; values are low, but the car itself is a genuine seven-seat off-roader.
Mercedes replaced the naturally aspirated M273 V8 with the M278 biturbo for better power and efficiency. The AMG GLS 63 (M157) arrived as the ultimate performance SUV — 557 PS in its original form.
The M278 is a significant step up in power (455 PS vs 388 PS) but carries timing chain and turbocharger risks on higher-mileage examples. The M157 AMG V8 is robust but expensive to maintain.
Mercedes standardised the "GL" naming convention for SUVs — the GL-Class became the GLS, aligning with the S-Class as the flagship. The facelift brought updated electronics, better interiors, and mild powertrain refinements.
The 2016 facelift is the sweet spot — better rust protection, better electronics, and the GLS nameplate. The OM642 diesel remains the smart choice; the V8s are for those who prioritise power over economy.
The X167 moved to Mercedes' MRA platform, bringing the latest engine families (M256, M176, M177) with 48V mild-hybrid systems. The inline-six replaced the V6 diesel; the V8s gained more power and better efficiency.
The M256 and M176 are modern, efficient, and well-regarded. The AMG GLS 63 (M177) is a 600+ PS missile. But these are £80,000–£120,000+ cars — replacement costs are high, but values are high enough to absorb them.
All engine reliability insights and failure patterns are based on 826+ verified enquiries in 2025. Data covers the UK market. [BMW-VERIFIED]
Different buyers, different priorities. Here is our verdict on who the GLS is perfect for - and who should think twice.
The GLS is one of the few genuine seven-seat luxury SUVs — and arguably the best. The X166 with the OM642 diesel is the sweet spot: space for seven, 35+ mpg on a run, and enough towing capacity for a caravan or horsebox. The X167 is even better but costs four times as much.
If you want the most luxurious seven-seat SUV on sale, the X167 GLS — especially the Maybach version — is the benchmark. The M176 V8 is smooth, effortless, and quiet; the interior is a masterpiece. The X166 is also a luxury car, but the X167 is in a different league.
The GLS is a genuine tow car — up to 3,500 kg on most variants. The OM642 diesel is the best choice for towing; the V8s have the power but are thirstier. The X166 with the OM642 is a superb towing machine — comfortable, stable, and reliable if maintained.
The GLS 63 AMG (M157 in the X166, M177 in the X167) is a 577–612 PS SUV that can out-accelerate most sports cars. The X166 GLS 63 is a used bargain at £20,000–£35,000 — but budget for £6,000–£10,000 for an engine replacement if it goes wrong. The X167 GLS 63 is £100,000+ but is one of the fastest SUVs ever built.
The X164 GL-Class is entering classic territory — the first-generation full-size Mercedes SUV. The X166 GLS 63 AMG is also a future classic — the first AMG version of the flagship SUV. Buy the cleanest X166 GLS 63 you can find and hold onto it. The X167 is a keeper too, but it's still depreciating.
Real talk. The right GLS for you depends on your budget, your mileage, and your patience for maintenance. Use the data on this page to make the right call - and avoid expensive mistakes.
The GLS's biggest decision isn't which engine to buy — it's whether to fix the one you already have.
If your OM642 is leaking oil from the cooler seals, or your M278 is rattling on cold start, get a diagnosis before deciding. A £800 oil cooler seal repair is very different from a £6,000 full replacement.
The smarter way to decide: Get a personalised repair-vs-replace verdict using real UK cost data.
Launch the BMW diagnostic calculator with GLS pre-selected.
We'll identify it first.
Identification is the first step inside the tool.
We'll pinpoint your exact engine code before running the diagnostics.
Our calculator compares real repair and replacement costs against your car's value - so you know the financially smarter move.
Built on Real Data - Every reliability rating and cost range on this page comes from genuine UK enquiry and quote data — not manufacturer marketing, not forum guesswork. The GLS's data is drawn from real owner enquiries and cross-referenced against Mercedes-Benz specialist sources [PATTERN DATA].
We Tell You When Not to Repair - The GLS's economics swing means we tell you when a repair doesn't make sense. A £3,200 OM642 recon on a £8,000 X164 is a tough call; a £6,000 M157 recon on a £15,000 GLS 63 is a major decision — and we say so. That's the difference between a knowledge base and a sales page.
Vetted Mercedes - Benz Specialists — 25+ vetted Mercedes-Benz specialists who work on GLS engines daily. They know the OM642 oil cooler seals, the M278 timing chains, and the M157 turbochargers inside out — and they'll give you an honest assessment before they touch your car.
Part of Engine Finders - MercedesEngines.uk is part of the Engine Finders family, the UK's leading engine replacement marketplace — giving you the research depth of an independent authority with a vetted route to action when you need one.
Read our in-depth BMW 3 Series vs 5 Series reliability guide.
Everything you need to choose with confidence.
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