Increase in fuel consumption: which faults cause it?

The most important among the documented faults: EGR and particulate filter clogging, and emissions software updates, in the OM651; turbo and wastegate valve failure, in the BMW N47; loss of power and turbo faults, in the BMW M47; N53 piezoelectric injector failure, in the BMW N52 / N53; injection pump or injector failure, in the 2.2/2.5 dCi; emissions defeat device (AdBlue/EGR) and software update campaign, in the OM642; clogged diesel particulate filter (DPF) and oil dilution, in the 1.7 CDTI; piezo injector wear and failure, in the 2.2 HDi.

Consumption and fluid levelsUrgency: Monitor

Increase in fuel consumption: causes and the faults that trigger it

Before suspecting a fault, check the simple things: tyre pressure, extra weight or a roof rack, air conditioning use and whether the way you drive has changed. If consumption stays clearly above normal over several tanks with similar journeys, the sources point to injectors, the lambda sensor, other sensors, the air filter, spark plugs or wheel alignment, and recommend a diagnostic check.^[1][2][3]

31 documented faults cause it in 26 engines. The most important:

High severity: EGR and particulate filter clogging, and emissions software updates · OM651
High severity: Turbo and wastegate valve failure · BMW N47
High severity: Loss of power and turbo faults · BMW M47

What it means

A rise in consumption without any change in use may be caused by faulty injectors, sensors sending wrong data, frequent particulate filter regenerations or a thermostat that stops the engine reaching its operating temperature.

General explanation from MotorFiable. How it shows up in each engine, with sources, is in the list of faults.

What to do now

Monitor

Compare real consumption over successive fill-ups and ask for a diagnosis if the increase is more than 10-15% with no explanation.

Reviewed on 29 October 202638 sources How we work

Most common causes

From most to least likely according to the sources. Under each cause, the part and the related OBD codes.

1. Under-inflated tyres
Common cause
GnG presents it as one of the simplest and most frequent causes: lower pressure increases rolling resistance and wear. It cites the IDAE (Spain's energy-saving agency), according to which driving with 0.3 bar less than specified means about 3% extra consumption. Veiko and the Araujo garage also include it.^[1][2][3]
Faults with with tyres and wheels
2. Change in use: city driving, short journeys, harsh driving
Common cause
GnG reminds us that traffic jams, short journeys with a cold engine, frequent acceleration, load and climate control raise consumption without any fault, and that two consecutive tanks can differ without a mechanical problem. Veiko puts the effect of harsh acceleration and braking at up to 20%.^[1][2]
3. Extra weight, roof rack or roof box, air conditioning
Common cause
GnG cites unnecessary items in the boot and, above all, roof racks, roof boxes and bike carriers, which worsen aerodynamics at road speed. Veiko says that overusing the air conditioning in town can raise consumption by up to 10%.^[1][2]
Faults with with the air conditioning
4. Dirty air filter or overdue maintenance
Possible cause
GnG and Veiko explain that a clogged air filter hampers efficient combustion, and GnG adds that delaying oil and filter changes or using an oil that doesn't meet the specification makes the engine work less efficiently.^[1][2][3]
Faults with with oil consumption
5. Dirty or faulty injectors
Possible cause
According to Araujo, a faulty injector can deliver too much fuel or deliver it unevenly and usually causes jerking, hard starting or an unstable idle. Veiko includes them along with worn spark plugs, a clogged fuel filter and the fuel pump, and GnG cites them among the elements that can send consumption soaring.^[1][2][3]
Faults with with the injectors Faults with with the fuel pump Faults with with the ignition coils
6. Lambda sensor and engine management sensors
Possible cause
Araujo says that a failing lambda sensor can make the control unit inject more fuel than necessary without lighting any warning light, with a slight loss of power or jerking. GnG adds that a sensor giving a wrong reading makes the management less efficient, sometimes with no warning on the dashboard.^[1][3]
Faults with with the engine sensors Faults with with the control units P0171 P0172
7. Incorrect alignment or a brake that doesn't release
Possible cause
GnG says that incorrect alignment increases rolling resistance and that a brake component that doesn't release properly holds the car back; the car feels heavier, pulls to one side or wears the tyres badly.^[1]
Faults with with tyres and wheels Faults with with brake calipers and discs
8. Fuel leak
Uncommon
Veiko calls it uncommon: leaks from the tank, hoses or connections lose real fuel, sometimes without the driver noticing.^[2]
Faults with with fuel leaks
9. Exhaust system faults
Uncommon
Araujo includes exhaust system faults among its eight reasons for higher consumption and Veiko recommends checking the catalytic converters and exhaust when consumption stays high after correcting the obvious.^[2][3]

Depending on what you notice

It uses more fuel and I do the same journeys

GnG asks you to look at the trend, not a single tank: if over several weeks or refuels consumption is clearly above normal on similar routes, it is worth looking for the cause.^[1]

It uses more fuel, with jerking or an unstable idle

Araujo associates jerking, hard starting or an unstable idle with faulty injectors, and GnG advises a diagnostic check if loss of power, abnormal smoke, vibrations, smells or a warning light also appear.^[1][3]

It uses more fuel in town or when cold

GnG cites urban journeys, traffic jams and very short trips with a cold engine among the uses that raise consumption, and Veiko mentions extreme climates as an external factor.^[1][2]

It uses more fuel with a roof rack, roof box or loaded boot

GnG explains that extra weight demands more energy when pulling away and accelerating and that roof racks, roof boxes and bike carriers worsen aerodynamics; removing them recovers some of the efficiency.^[1]

It uses more fuel and the tyres wear oddly

Araujo points to uneven wear and a heavier driving feel as the first signs of incorrect pressure, and GnG adds that poor alignment wears the tyres and can make the car pull to one side.^[1][3]

What to check first

Note litres and kilometres between fill-ups (or look at the average consumption on the trip computer) to compare with your own history: GnG considers that comparison more reliable than the official figure.^[1]
Measure tyre pressure when cold, with the load and values specified by the manufacturer; it is the cheapest check and, according to GnG and Veiko, one of the most frequent causes.^[1][2]
Remove whatever isn't needed: roof rack, roof box, bike carrier or weight in the boot, and look at your air conditioning use and the way you drive.^[1][2][3]
Check that the filters (air, fuel), the oil and the spark plugs, on engines that have them, are up to date according to the manufacturer's schedule.^[1][2]
If the increase exceeds normal variation and persists, ask for a diagnostic check with fault-code reading and a check of the injectors, lambda sensor and sensors, as well as alignment and brakes.^[1][3]

Can I keep driving?

Urgency: Monitor

An increase in consumption on its own doesn't mean you have to stop driving the car. The sources recommend taking it to the garage if the increase is clear, persists over several tanks and isn't explained by use, or if it comes with loss of power, jerking, hard starting, abnormal smoke, vibrations, smells or a warning light. Veiko reminds us that a fuel leak loses real fuel, so if you notice a smell or stains it should be checked as soon as possible.^[1][2]

Documented faults that cause it

Specific engine and gearbox faults, from most to least important (severity × frequency). Below each title, how the symptom shows up in that fault.

- High severityFrequency: Very frequentOM651EGR and particulate filter clogging, and emissions software updatesHigher fuel consumption, which several owners link to the emissions software update.Repair (garage): €800–€2,500
Source for the symptom in the OM651^[4]
- High severityFrequency: CommonBMW N47Turbo and wastegate valve failureA noticeable increase in fuel consumption when the wastegate is left partially open.Repair (garage): €900–€1,800
Source for the symptom in the BMW N47^[5]
- High severityFrequency: CommonBMW M47Loss of power and turbo faultsHigher fuel consumption when the turbo does not reach the right boost pressure.
Source for the symptom in the BMW M47^[6]
- High severityFrequency: CommonBMW N52 / N53N53 piezoelectric injector failureHigher fuel consumption.
Source for the symptom in the BMW N52 / N53^[7]
- High severityFrequency: Common2.2/2.5 dCiInjection pump or injector failureIncreased consumption when an injector sprays the fuel incorrectly.
Source for the symptom in the 2.2/2.5 dCi^[8]
- Medium severityFrequency: Very frequentOM642Emissions defeat device (AdBlue/EGR) and software update campaignSome owners report an increase in AdBlue or fuel consumption after installing the campaign's software update, although no official figure has been published.
Source for the symptom in the OM642^[9]
- High severityFrequency: Occasional1.7 CDTIClogged diesel particulate filter (DPF) and oil dilutionFuel consumption much higher than normal, both in town and on the motorway, according to the account of the Astra with this engine.
Source for the symptom in the 1.7 CDTI^[10]
- High severityFrequency: Occasional2.2 HDiPiezo injector wear and failureIncreased diesel consumption.
Source for the symptom in the 2.2 HDi^[11]
- Medium severityFrequency: Common1.6 CRDiParticulate filter (DPF) blocked in urban useIncreased fuel consumption during active regeneration attempts.Repair (garage): €300–€1,800
Source for the symptom in the 1.6 CRDi^[12]
- Medium severityFrequency: CommonBMW N43/N46Injector, ignition coil and NOx sensor failures (N43)Higher fuel consumption when the NOx sensor forces the engine to leave lean-burn operation more often than normal.
Source for the symptom in the BMW N43/N46^[13]
- Medium severityFrequency: Common1.0 T-GDICarbon build-up on the intake valves and coking of the injectorsIncreased fuel consumption with no apparent explanation.
Source for the symptom in the 1.0 T-GDI^{[14][15][16][17][18]}
- Medium severityFrequency: Common1.7 CRDiParticulate filter (DPF) clogged in urban useIncreased fuel consumption during active regeneration attempts.Repair (garage): €250–€1,200
Source for the symptom in the 1.7 CRDi^[19]
- Medium severityFrequency: Common2.2 CDI (OM646)EGR valve clogged or seized by sootIncreased fuel consumption when the valve does not close properly, according to the testimonies collected.
Source for the symptom in the 2.2 CDI (OM646)^[20]
- Medium severityFrequency: Common2.0 dCiClogged particulate filter (DPF)Higher consumption from frequent regenerations, which inject extra fuel to burn off the accumulated soot.
Source for the symptom in the 2.0 dCi^[21]
- Medium severityFrequency: Common2.0 dCiInjector failureHigher consumption when an injector sprays incorrectly and combustion becomes less efficient.
Source for the symptom in the 2.0 dCi^[22]
- Medium severityFrequency: Common2.0 FSICarbon build-up on the intake valvesHigher fuel consumption as carbon deposits reduce the airflow past the valves.
Source for the symptom in the 2.0 FSI^[23]
- Critical severityFrequency: Rare1.5 BlueHDiDiesel leak at the common rail (2026 recall)Higher than normal diesel consumption.Repair: €0
Source for the symptom in the 1.5 BlueHDi^[24]
- Medium severityFrequency: Occasional1.6 dCiBlocked diesel particulate filter (DPF)Fuel consumption rises because the engine forces more frequent regenerations to try to clean the filter.Repair (garage): €600–€1,500
Source for the symptom in the 1.6 dCi^[25]
- Medium severityFrequency: Occasional1.6 and 2.0 MultiJet IIInjector faults and DPF particulate sensor failureIncreased fuel consumption associated with injectors that have lost atomisation.
Source for the symptom in the 1.6 and 2.0 MultiJet II^[26]
- Medium severityFrequency: Occasional2.0 / 2.4 GDI and T-GDI (Theta II)Carbon build-up on the intake valves of direct-injection Theta II enginesSlightly higher fuel consumption.
Source for the symptom in the 2.0 / 2.4 GDI and T-GDI (Theta II)^[27][28]
- Medium severityFrequency: Occasional2.0 CDI (OM640)Carbon build-up in the injectorsIncreased fuel consumption when the injector spray pattern stops being optimal.
Source for the symptom in the 2.0 CDI (OM640)^[29]
- Medium severityFrequency: Occasional2.2/2.5 dCiClogged EGR valveIncreased consumption if the EGR continuously alters the air-fuel mixture.
Source for the symptom in the 2.2/2.5 dCi^[30]
- Medium severityFrequency: Occasional1.4 and 1.6 TU3/TU5Thermostat stuck open or closedIf the thermostat sticks open, the engine does not reach its working temperature and uses more fuel than usual.
Source for the symptom in the 1.4 and 1.6 TU3/TU5^[31]
- Medium severityFrequency: Occasional2.4 / 2.8 D-4D (GD)Blocked particulate filter (DPF) due to incomplete regenerationsHigher fuel consumption.
Source for the symptom in the 2.4 / 2.8 D-4D (GD)^[32][33]
- Medium severityFrequency: OccasionalVM Motori 2.8 and 3.0 CRDWear of the injectors and the high-pressure pumpHigher than normal fuel consumption (1-2 l/100 km more on the 2.8, according to one source) with a faulty injector.Repair (garage): €800–€1,400Appears at around 120,000 km
Source for the symptom in the VM Motori 2.8 and 3.0 CRD^[34][35]
- Medium severityFrequency: OccasionalDrive-E gasolinaCarbon build-up on injectors and intake valves due to direct injectionA coked injector can meter fuel badly and increase consumption.
Source for the symptom in the Drive-E gasolina^[36]
- Low severityFrequency: CommonBMW N13Carbon build-up on direct injection injectorsIncreased fuel consumption if the injectors' spray pattern deteriorates.
Source for the symptom in the BMW N13^[37]
- Low severityFrequency: Common1.4 and 1.6 TU3/TU5Sensors that fail: lambda sensor and temperature sensorAn unstable idle and slightly higher fuel consumption are common when the lambda sensor or the temperature sensor sends an incorrect reading to the ECU.Appears at around 25,000 km
Source for the symptom in the 1.4 and 1.6 TU3/TU5^[31]
- Low severityFrequency: Occasional1.0 TSI / 1.5 TSICarbon build-up on the intake valvesIncreased petrol consumption.Appears at around 80,000 km
Source for the symptom in the 1.0 TSI / 1.5 TSI^[38]
- Low severityFrequency: OccasionalVM Motori 2.8 and 3.0 CRDEGR valve and intake clogged with sootHigher than normal fuel consumption if the EGR is clogged, according to one source.Repair (garage): €150–€600
Source for the symptom in the VM Motori 2.8 and 3.0 CRD^[34]
- Low severityFrequency: Rare2.2/2.5 dCiDirty or misreading mass airflow sensorIncreased consumption when the air-fuel mixture stops being adjusted correctly.
Source for the symptom in the 2.2/2.5 dCi^[30]

Which cars it appears in

These faults affect 26 engines. We have documented 211 models from 27 makes with some of the affected versions: open yours to see all its faults.

Engines

Cars with the affected versions

Alfa Romeo

Audi

BMW

See all BMW models

Chrysler

Citroën

See all Citroën models

Cupra

Dodge

Dodge NitroEngine: VM Motori 2.8 and 3.0 CRDYears: 2007–2011

DS

DS DS 4 IIEngine: 1.5 BlueHDiYears: since 2021

Fiat

Ford

Ford Mondeo IVEngine: 2.2 HDiYears: 2007–2014

Hyundai

See all Hyundai models

Infiniti

Jeep

Kia

See all Kia models

Lancia

Land Rover

Mercedes-Benz

See all Mercedes-Benz models

MINI

Nissan

Opel

Toyota

Volkswagen

See all Volkswagen models

Volvo

See all Volvo models

Uses more fuel: causes in your car

211 cars have several documented faults that cause this symptom. Choose yours to see only those that affect it, by engine and by year.

Alfa Romeo 3

Audi 8

BMW 10

Chrysler 4

Citroën 13

Cupra 2

Dodge 1

Dodge Nitro

DS 1

DS DS 4 II

Fiat 8

Ford 1

Ford Mondeo IV

Hyundai 13

Infiniti 2

Jeep 7

Kia 19

Lancia 2

Land Rover 2

Mercedes-Benz 24

MINI 3

Nissan 7

Opel 8

Peugeot 12

Renault 11

Seat 10

Škoda 11

Toyota 2

Volkswagen 17

Volvo 10

Uses more fuel by brand

Fault codes that may go with it

If you have an OBD reader, the code stored by the control unit helps you work out which system is failing.

Frequently asked questions

How much fuel should my car use?

GnG explains that there is no figure valid for everyone: it depends on the engine, weight, aerodynamics, traffic, temperature, load and driving, and that the official figure need not match the real one. The best reference is your own history.^[1]

When should I take it to the garage for high consumption?

When the increase is clear, persists over several fill-ups on similar routes and has no explanation, or if other symptoms such as loss of power, jerking or a warning light appear, according to GnG. Veiko adds that, if it stays high after correcting your habits, a professional check is advisable.^[1][2]

How much extra fuel does low tyre pressure cause?

GnG cites the IDAE: about 0.3 bar below the specified pressure means roughly 3% extra consumption.^[1]

Can a fault raise consumption without lighting any warning light?

Yes. Araujo explains that the lambda sensor can fail without lighting the warning light, and GnG that sometimes the only sign is that the car uses more fuel. A diagnostic check with a code reader helps direct the inspection.^[1][3]

How much does it cost to fix high consumption?

It depends entirely on the cause, from inflating the tyres or removing the roof rack to cleaning or replacing injectors or the lambda sensor. The sources consulted don't publish prices, so we give no figures.^[1][3]

Does the air conditioning affect consumption?

Veiko says that overusing it, especially in town, can increase consumption by up to 10%. GnG also mentions it among the usage factors.^[1][2]

Other symptoms: consumption and fluid levels

All symptoms

Has this happened to you? Tell us which fault it was, at how many kilometres and how much you paid: it helps other owners know what to expect. Report your fault.

Sources

Every fact on this page links to its source. If you find an error, let us know.

¿Por qué mi coche consume más combustible? 7 causas que deberías revisarGnG · Other source · published 17 September 2026 · consulted 29 October 2026 · in Spanish
¿Por qué mi coche tiene un consumo más elevado de lo normal?Veiko · Other source · published 14 August 2025 · consulted 29 October 2026 · in Spanish
8 razones por las que tu coche consume más combustible de lo normalElectromecánica Araujo · Other source · consulted 29 October 2026 · in Spanish
Mercedes OM651: Typische Probleme und HaltbarkeitGebrauchtwagenberater · Motoring press · consulted 26 September 2026 · in German
Problemas del motor N47 BMWEcorecambios · Technical documentation · consulted 26 September 2026 · in Spanish
Motor BMW M47: problemas y averíasDasercars · Technical documentation · consulted 27 September 2026 · in Spanish
BMW N53 Engine ProblemsBMW Tuning · Other source · consulted 5 October 2026
Fiabilité Nissan Primera : pannes et avisFiches-auto.fr · Motoring press · consulted 27 September 2026 · in French
Mercedes OM642: Zuverlässiger Dauerläufer oder Kostenfalle?Gebrauchtwagenberater · Motoring press · consulted 26 September 2026 · in German
Essai complet Opel Astra (H) : fiabilité et avisFiches-auto.fr · Owners' forum · consulted 27 September 2026 · in French
Essai, avis et fiabilité des 2,2 HDI 136 chevauxFiches-Auto · Motoring press · consulted 27 September 2026 · in French
Kia Ceed 1.6 Crdi Problemas | Fallos y averías más frecuentesTotalRenting · Other source · consulted 26 September 2026 · in Spanish
BMW N43: Bei diesem Benziner ist Ärger vorprogrammiertGebrauchtwagenberater · Motoring press · consulted 27 September 2026 · in German
Hyundai i20 III: Bekannte Schwachstellen & RückrufeGebrauchtwagenberater · Other source · consulted 27 September 2026 · in German
Hyundai i30 III: Typische Probleme und KrankheitenGebrauchtwagenberater · Other source · consulted 27 September 2026 · in German
Hyundai Kona: Bekannte Probleme & KaufberatungGebrauchtwagenberater · Other source · consulted 27 September 2026 · in German
Kia Stonic (YB): Bekannte Probleme, Mängel & KaufberatungGebrauchtwagenberater · Other source · consulted 27 September 2026 · in German
Kia Rio IV (seit 2017): Typische Probleme & SchwachstellenGebrauchtwagenberater · Other source · consulted 27 September 2026 · in German
Hyundai iX35 1.7 Crdi Problemas | Fallos y averías más frecuentesTotalRenting · Other source · consulted 27 September 2026 · in Spanish
Fiabilité 220 CDIFiches-auto.fr · Motoring press · consulted 27 September 2026 · in French
Fiabilité Renault Espace 4 : pannes et avisFiches-auto.fr · Motoring press · consulted 27 September 2026 · in French
Fiabilité Renault Koleos : pannes et avisFiches-auto.fr · Motoring press · consulted 27 September 2026 · in French
VW Passat B6 – Bekannte Probleme & SchwachstellenGebrauchtwagenberater.de · Motoring press · consulted 27 September 2026 · in German
1.5 BlueHDi. Stellantis rappelle plusieurs milliers de véhicules pour un problème d'injectionL'argus · Motoring press · published 14 March 2026 · consulted 26 September 2026 · in French
Las 10 averías del coche más caras en 2026: cuánto cuesta cada reparaciónMotorpoint · Motoring press · published 2026 · consulted 27 September 2026 · in Spanish
Fiat Doblò: problemas, fallos y averías más frecuentesTotalrenting · Other source · consulted 27 September 2026 · in Spanish
Kia Sorento II (2009 – 2014) – Typische Probleme & KrankheitenGebrauchtwagenberater · Other source · published 7 April 2023 · consulted 8 October 2026 · in German
What Parts Of The Engine Are The Most Prone To Carbon Buildup?SlashGear · General press · published 10 May 2026 · consulted 8 October 2026
Mercedes A-Klasse (W169) – Typische Probleme & SchwachstellenGebrauchtwagenberater · Motoring press · consulted 27 September 2026 · in German
Fiabilité Nissan Almera : pannes et avisFiches-auto.fr · Motoring press · consulted 27 September 2026 · in French
Tous les problèmes sur Citroën C2 (témoignages)Fiches-auto.fr · Owners' forum · consulted 27 September 2026 · in French
Toyota's DPF problems are a symptom of stringent emission regulations4X4 Australia · Motoring press · published 5 January 2020 · consulted 9 October 2026
Toyota Faces Up To $1.5 Billion Payout To Owners Over Diesel Lawsuit In AustraliaCarscoops · Motoring press · published 7 April 2022 · consulted 9 October 2026
Problemas Jeep Wrangler 2.8 CRDTotal Renting · Other source · consulted 8 October 2026 · in Spanish
Jeep Grand Cherokee WK2 con kilometraje: se puede comprar, pero con maticesZa Rulyom (zr.ru) · Motoring press · published 28 April 2023 · consulted 8 October 2026 · in another language
Volvo V90 – Bekannte Probleme & KrankheitenGebrauchtwagenberater.de · Other source · published January 2024 · consulted 27 September 2026 · in German
Tickende Zeitbombe: So zuverlässig ist der Prince-Motor von PSA und BMWGebrauchtwagenberater.de · Motoring press · published 13 March 2026 · consulted 27 September 2026 · in German
Del 1.9 TDI al 1.5 TSI, así es el motor que ha cambiado la historia reciente de VolkswagenMotor.es · Motoring press · published 7 June 2026 · consulted 26 September 2026 · in Spanish