Excessive fuel consumption of your engine may be due to your driving style, but if the fuel consumption is significantly too high, there is usually a defect. It is often not easy to determine this. If this is the case, the car must be taken to a workshop.
Even without a fault, the consumption changes of course according to the load. Several passengers and a lot of luggage make it significantly higher than when driving with a single driver, a roof rack and a lack of air in the tires also increase it. In addition, driving style and route play a very important role. In city traffic with many “stops
If there is a defect, you will notice it in the heavily modified consumption. The engine suddenly swallows much more, even if you drive alone in summer and without a load at 90 km/h on the country road. Sometimes a defect (such as the lambda sensor) changes fuel consumption quite slightly, in other cases your vehicle suddenly consumes almost twice as much fuel as usual. This should be noted. You must now immediately determine the cause.
First, check the tire pressure (up to 30% more fuel consumption if the pressure is too low) and also look for loose trim in the wheel wells or under the vehicle. Often these are not visible and do not cause noise, but they do cause much higher fuel consumption due to higher air resistance. Finally, a very dirty air filter can increase your engine’s fuel consumption.
If you have been able to exclude or eliminate the causes mentioned, which are rather simple causes, and the consumption is still far too high, the vehicle should generally be taken to the workshop. The workshop was able to find the following causes :
Defective brake piston:
This causes the brake to jam, which naturally increases consumption due to the increased resistance.
Defective bearings :
All bearings on which the wheels as well as the motor and transmission shafts rotate lead to higher consumption in the event of a defect. Sometimes it can also be heard (squeaking and rubbing noises).
Clogged injection nozzles :
You can hardly diagnose this fault yourself. The engine has one injection valve per cylinder (injector in the case of diesel), which supplies the fuel mist. The nozzles become clogged over time, which gradually reduces the efficiency of the engine. It must “pull more fuel” to continue to deliver the required power. The problem is not too precarious; it can be repaired in the workshop at a relatively low cost. In some cases, it is sufficient to add special additives to the fuel. But this must be decided by your shop, as the additive must be approved for your vehicle. If the deposits are stubborn, the shop will usually remove and clean the injectors.
Defective auxiliary unit :
The air conditioning compressor or alternator may be defective, even if the engine needs a lot more power. When the compressor is turned on, it is driven by a magnetic clutch via a V-belt, which means more resistance for the engine. Air conditioning operation can mean between 0.5 and 2.5 liters of extra fuel consumption per 100 km. If the magnetic clutch is defective, the compressor is not stopped. This means that the increased resistance is maintained at all times. Even modern alternators are decoupled under load, but this decoupling can fail.
Then consumption also increases. In addition to the solenoid valve, a bearing or pulley may be defective. This makes it more difficult to operate the generator, the engine has to cope with increased operating resistance. If such a fault occurs, you will sometimes hear it, even with aggregates running, by unusual and altered noises.
Fault in the electronic motor control unit :
The control unit may be faulty or it may receive incorrect signals from a sensor. This can lead to excessive fuel injection.
There are fairly innocuous and even relatively quick ways to remedy the causes of excessive consumption. In some cases, however, you may need to take the car to the garage. Repair is also important because higher fuel consumption may be associated with increased wear and tear on certain parts.