Consumption
Car uses more fuel than normal: causes and what to check
If the car uses more fuel although you drive it the same way, something is making it work harder or burn worse. The usual causes are under-inflated tires, an engine that does not reach its temperature (thermostat), sensors that upset the mixture, dragging brakes or, on diesels, frequent particulate filter regenerations.
Check without hurryConsumption
Reviewed by Daniel Morales, founder of Reprorace SL, on
Is it serious? Can I keep driving?
Usually not urgent, but do not ignore it. It is not urgent, but it is a useful warning: many faults that do not light a warning yet show first in consumption. Have it checked at your next garage visit.
A careful, general answer: only someone who inspects the car can say whether it is safe to drive. When in doubt, stop somewhere safe and call for assistance.
Most likely causes
- Under-inflated tires: they increase rolling resistance; the simplest thing to correct.
- Thermostat stuck open: the engine is slow to warm or never reaches temperature and the mixture is enriched.
- Oxygen sensors or air-flow meter: a wrong reading upsets the mixture.
- Dragging brakes: a sticking caliper brakes the car all the time.
- Use and conditions: short trips, cold, load, a roof box or air conditioning raise consumption with no fault.
Listed from more to less common in general; on your car they may be different. A fault-code reading and a check at the garage confirm which one it is.
To understand it better: What are fuel trims and how do you read them? What is an oxygen sensor and when does it fail? What does the engine thermostat do and what does P0128 mean?
Car system: Fuel and air
What you can check yourself
Measure consumption from full tank to full tank rather than relying only on the trip computer.
Set the tire pressures cold.
See whether the temperature gauge takes very long to rise or stays low.
Remove weight and roof bars you do not use and compare over a few days.
Safe checks only: with the engine off and cold whenever you look under the hood, without taking anything apart and without touching hot or moving parts.
Related fault codes
- P0171Mixture too lean (bank 1)
- P0172Mixture too rich (bank 1)
- P0128Coolant thermostat: coolant temperature below the thermostat regulating temperature
- P0101Mass or volume air flow sensor A, circuit: range/performance
- P0133O2 sensor (bank 1, sensor 1), circuit: slow response
- P0300Random or multiple cylinder misfire detected
Generic codes that often come with this symptom. Seeing one does not confirm the cause: it is where the diagnosis starts.
How the ECO-LITE helps diagnose it
Plugged into the OBD socket, the ECO-LITE reads the fault codes of the control units that answer, with the freeze-frame data captured when the fault happened, and shows live data on your phone or computer. With your permission, your garage can see them remotely before you bring the car in.
What to look at here: coolant temperature, fuel trims, oxygen sensors, air flow and, on diesels, how often it regenerates.
Frequently asked questions
Is the trip computer's consumption reliable?
It is good for comparisons, but it can be off. To spot a fault, measure from full to full several times.
Does cold weather increase consumption?
Yes: the engine takes longer to warm up, the oil is thicker and more loads are used. A rise in winter is normal.
Which codes usually appear?
P0128 (thermostat), P0171 or P0172 (mixture) and P0101 (air-flow meter) are common when consumption rises because of a fault.
Keep reading
- Fuel and air: how it works and what fails
- Particulate filter regenerating too often: causes
- Tire pressure warning light on: what to do
- Black smoke from the exhaust: causes and what to do
- Car symptoms: what they mean and what to do
- Check engine light on: what to do
- How to read and clear your car's fault codes
- OBD fault codes: what each one means