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A sudden increase in fuel consumption almost always indicates poor combustion: the ECU compensates by injecting more fuel. Before thinking about the engine, though, the trivial causes must be ruled out.

Quick checks

• Tyre pressure and uneven wear
• Clogged air filter
• Roof bars or extra load
• Changed routes: many short trips use much more fuel
• Air conditioning always on and heavy traffic

Most common technical causes

• Lazy or faulty lambda sensor: the mixture stays rich
• Injectors leaking or with flow out of specification
• Thermostat stuck open: the engine stays cold and enriches
• DPF regenerating continuously
• Slipping clutch or binding brakes
• MAF sensor under-reading the air flow

What to do right away

• Measure real consumption at fill-ups, not just from the trip computer
• Have the fuel trims (short and long term) read: they show whether the ECU is compensating
• Check the operating temperature: if it stays low, suspect the thermostat

How MasterTuning helps

We do not replace parts by trial and error: we read the real values from the ECU (pressures, flow rates, corrections, temperatures) and identify the component responsible. Then we repair and recalibrate the software where needed. Centres throughout Italy.

Read more: vehicle database · what is ECU remapping · original files archive

Does your car have this symptom? Book a diagnosis at your nearest MasterTuning centre.

Frequently asked questions

Why do I use more fuel in winter?

The engine takes longer to reach operating temperature and in the cold phase the mixture is richer: with short trips the increase is considerable.

Does the lambda sensor affect fuel consumption?

A lot: a lazy or faulty sensor makes the engine run with a rich mixture, increasing consumption and emissions.

How do you tell whether the injectors are using too much fuel?

With a flow and return test and by reading the ECU’s injection corrections.