If you try to group all possible causes of increased fuel consumption, then there will be only two of them. First, the engine is running inefficiently. Simply put, some of the gasoline, diesel or gas is wasted. The second global reason is when something interferes with the movement of the car. That is, there is some harmful resistance, to overcome which the engine burns additional fuel. But there is also one unique reason that does not belong to any of the groups described. Let's start with her.
Reason 1. Incorrect estimation of fuel consumption
What makes you think that fuel consumption has increased? Let's consider several options:
- The overrun is displayed on the on-board computer.
- It seems to you that on filled n liters the car should have traveled more kilometers than it turned out in fact.
- You have measured the flow rate manually. For example, they filled a full tank, drove a certain distance, refueled again, and determined the consumption by the volume of fuel added.
- You constantly monitor fuel consumption by recording each refueling and odometer readings in a notebook or a special mobile application.
So, only with the fourth option, you can start to panic. All other situations do not have sufficient accuracy and objectivity to speak with confidence about increased fuel consumption. The on-board computer can lie, especially if it is freelance. The second and third options are, so to speak, disposable. They lack objectivity, unless repeated several times in a row with the same results.
Regular accounting, based on the actual volumes of fuel burned and kilometers traveled, is a completely different matter. If the figures obtained in this way show an overrun, then there are no options - you need to look for the reason. It is not so difficult if you know what to pay attention to in the first place. It is to these factors that this article is devoted.
Read more - how to calculate fuel consumption correctly.
Reason 2. Low-quality fuel
A very common cause of increased fuel consumption at all times of the existence of the car. Poor-quality fuel is sometimes filled even at the most trusted gas stations that you visit regularly. At random gas stations that come across on the highway during long trips, stumbling upon poorly burning gasoline or diesel fuel turning into jelly is generally a common thing.
The biggest problem with this cause is that it is almost never noticed immediately after refueling. As a rule, if the fuel is not of completely disgusting quality, the overrun is noticed after many kilometers. Sometimes low-quality gasoline makes itself felt at all on the second day. In such cases, few people begin to sin at the gas station, blaming the car or secondary factors for the increased consumption.
This reason also has an advantage. The increased consumption disappears when low-quality fuel is produced, or its concentration in the tank decreases due to refueling with a new portion. That is why only with regular accounting can you start to panic about overspending. You know exactly what the average fuel consumption should be under certain circumstances, and if the numbers increase between refueling, you will immediately understand what is the reason.
In addition to the quality of the fuel, its consumption is also affected by the octane number, if it is gasoline. For example, if the engine of your car is designed for the 95th, and you decide to save money, bay 92nd, you are guaranteed an increased consumption. As a rule, the problem is accompanied by a decrease in throttle response and other signs of unsuitable fuel.
Reason 3. Inept or aggressive driving
Aggressive and calm driving are understood by many in different ways. The border looks like this. An aggressive driver starts briskly from a standstill, turns the engine up to 4-5 thousand revolutions to switch to the next gear, maintains a high speed to the last, and then intensively works out the brakes. The other driver starts to drive smoothly, does not press his slippers on the floor, shifts gears at the lowest possible speed, sees the stopping place in advance, releases the gas in a timely manner, uses engine braking more than the main brakes. At the same time, the second fuel consumption per 100 km is 7 liters, and the first has 15 liters.
Inept driving is a separate topic, which cannot be studied within the framework of this article. Let's leave only a few theses, relying on which, those who wish will be able to show curiosity and expand their knowledge:
- Spinning the engine past the maximum torque point (check your car's specifications) is a wild waste of fuel.
- Gear shifting at a speed of 2-2.5 thousand saves fuel.
- Engine braking is a great technique not only to save fuel, but also to improve safety.
- Coasting is not the best way to reduce fuel consumption.
- Any pressing on the brake pedal is the conversion of the energy generated by the engine into heat.
This list could be continued. But we have a different issue.
Read later how to change gears on the mechanics and save fuel.
Reason 4. Overload
An increase in the mass of the car directly affects the increase in fuel consumption. Everything is extremely simple here. To move any load, you need to spend energy. And the heavier this load, the more energy is needed. Accordingly, fuel consumption increases. It is believed that every additional 100 kg of weight carried increases gasoline consumption by 10%. That is, if four people are sitting in the cabin (except you, as the driver), plus the trunk is loaded with some things, then fuel consumption can easily increase one and a half times from the nominal one.
Reason 5. Driving with a trailer
A car trailer affects the increase in fuel consumption in a complex way. First, it's extra weight. Secondly, to the four wheels, which are characterized by rolling resistance, two more are added (or even four, if the trailer is two-axle). Thirdly, the trailer has an extremely negative effect on aerodynamics. That is, it literally slows down the car due to the frontal air resistance. It is also worth adding harmful air turbulences, which also “hold the car by the backside”.
On average, when driving with a trailer loaded in accordance with the rules for its operation, fuel consumption increases by at least one and a half times. And even at two. You also need to remember that the trailer also has some kind of running gear. At a minimum, there are wheels whose toe angle affects fuel consumption. Tire pressure matters a lot too. Even the equipment of the trailer affects fuel consumption. For example, an awning. A covered trailer has much better aerodynamics than an open trailer. Fuel consumption, respectively, can also vary quite decently from this.
Reason 6. Roof rack
Unlike a full-fledged trailer, the roof rack does not have wheels and such a lot of weight. On average, about 100-150 kg. Nevertheless, this is already a plus of 10-15% to fuel consumption, because the mass in this case works similarly. But much more on the consumption of gasoline affects the aerodynamics of the roof rack. This must be taken into account when choosing it, and during operation. Fortunately, today it is not difficult to choose for any car not only a roomy and aesthetically looking trunk, but also one that has a well-streamlined shape. Nevertheless, despite this, there will still be an overrun.
Reason 7. Low tire pressure
When the air pressure in the wheels of a car is below normal, the so-called contact patch changes significantly. This is the area where the tire is constantly in contact with the road surface. The larger the area of this same contact patch, the higher the rolling friction force. And this, in turn, means that it is “harder” for the engine to push the car forward. Accordingly, more fuel is required for a particular mileage.
Normal tire pressure for each vehicle is indicated in the owner's manual. Many people intentionally inflate their tires with high pressure, which, of course, allows you to save a little on fuel. However, such savings are not worthwhile, since over-inflated tires wear out faster. In addition, it should be remembered that too small a contact patch adversely affects the vehicle's handling. In particular, the braking distance increases, as well as the risk of drift or skidding when maneuvering.
Reason 8. Unadjusted wheel alignment
Toe and camber adjustments must be made at least twice a year. Usually, motorists deal with this issue when switching from winter tires to summer tires, and vice versa. Changed tires - visited a specialized service, and checked (adjusted) wheel alignment. Incorrectly installed wheels are a very important factor that increases fuel consumption. The reason is simple and clear. If the wheels do not “look” where the car is going, they additionally resist movement. In addition, the wear of the tires themselves is accelerated.
Especially often, regular wheel alignment adjustments are neglected by those motorists who have two sets of tires with discs available. When the season changes, tires change at home on their own, and no one goes to the service station, as this is extra money. This approach is fundamentally wrong. In addition, wheel alignment simply needs to be adjusted after buying a car and any (even minor) repair of the chassis or steering gear.
Reason 9. Driving on a cold engine
Today, there are often opinions that modern engines do not need warming up, and this does not affect fuel consumption in any way. In part, this is true. Over the past 20 years, technology has changed markedly. Motors are made not from cast iron, but from aluminum, the thickness of the parts has decreased, and they warm up much faster than before. But.
Even the most modern engine is not able to reach operating temperature instantly. It takes at least five minutes even in the summer. In the meantime, the engine is cold, it consumes more fuel than is written by the manufacturer in the technical specifications. If the car is of old years of production, and it’s not yet summer outside, then reaching the operating temperature and the most economical consumption takes more than 15 minutes. This is a proven fact, which is simply useless to dispute.
Quite visual tests have recently appeared on the Web, proving that an unheated engine is a good reason for increased fuel consumption. You can find them on You Tube for "cold fuel consumption".
Read later whether to warm up the engine.
Reason 10. Driving on winter tires in summer
Either in pursuit of dubious savings, or simply because of a lack of money, but the roads are full of cars “shod” in winter tires in summer. However, tires for winter use are made of soft rubber, and also have a higher tread with a fine, detailed pattern. All this impairs rolling on hard surfaces, respectively, resists movement. As a result, fuel consumption goes up.
In fairness, it should be said that driving in the summer on winter tires does not increase fuel consumption very much. Approximately 3-5%. But here we must also take into account that winter tires become too soft in summer, which increases the braking distance and worsens the car's handling. That is, it is also unsafe.
Reason 11. High load on the generator
The generator provides consumers with electricity while the car is moving. The battery is charged from it, the headlights are shining, the air conditioner is working, music is playing, and so on. The generator is driven directly from the engine, which is the harder it is to turn it, the greater the load from it is powered. And the heavier the engine, the more fuel it consumes. Accordingly, with each consumer turned on, fuel consumption increases.
For example, driving with headlights that have halogen or xenon bulbs requires 5-10% more gasoline than without them. If the lighting is LED, then it affects the consumption not so noticeably. Air conditioning is able to increase fuel consumption by 20-40%. Powerful acoustics (active subwoofers, numerous speakers, amplifiers, crossovers), an inverter for converting 12V to 220V and another powerful load on the generator are also guaranteed excessive fuel consumption.
Read more about alternator failures later.
Reason 12. Clogged air filter
The condition of the air filter affects how much air will flow into the fuel mixture preparation system. If it is clogged with dust, dirt, leaves, insects, and has not changed for several tens of thousands of kilometers, fuel consumption can increase up to 50%. Meanwhile, many motorists do not even know where this filter is, or simply forget about its existence under the hood.
Under normal vehicle operating conditions, it is recommended to change the air filter to a new one every 20 thousand km. If the car is often in dusty areas, used to drive through forests, dirt roads, and so on, replacement may be required every 5 thousand km. Fortunately, it costs a penny. Therefore, do not neglect these recommendations. Moreover, you will then save the money spent on the filter on fuel.
Reason 13. Low compression
Low compression causes the engine to run extremely inefficiently. The air-fuel mixture can neither compress normally in the combustion chambers nor give all the energy to the pistons during ignition and expansion. The main causes of low compression are wear on the piston rings, the pistons themselves, or the valves. Compression, by the way, may not be due to the weakening of the springs pressing the valves in their saddles, as well as due to the wear of the camshaft cams.
Reason 14. Problems with the ignition system
This reason applies only to gasoline engines. Including those who work together with HBO. There may be several problems:
- too early or late ignition;
- large or small gap between the electrodes of the spark plugs;
- failed or triggered candles every other time;
- punched high-voltage wires;
- failures in the computer.
In order for a gasoline engine to operate at maximum efficiency and consume a minimum of fuel, the spark must be timely and powerful enough. And in each of the cylinders. If one of the conditions is not met, fuel consumption increases.
Reason 15. Problems with the fuel system
For its work, any internal combustion engine uses not only fuel, but also air. And now, the consumption directly depends on the proportions and quantities in which the air-fuel mixture is supplied to the cylinders. The fuel system is responsible for its preparation. It can be carburetor or injection. For diesels, this is done by the injection pump. In modern engines, electronics are responsible for the operation of the fuel system. She, in turn, "focuses" on the signals of a dozen sensors. Failure of any of them can cause increased fuel consumption.
In carbureted engines, everything is much simpler and clearer. The main thing there is to properly adjust the preparation of the air-fuel mixture, as well as keep the jets clean.
Reason 16. Bad rollover
Even if you are not using coasting (in neutral), this setting still affects the vehicle's fuel economy. The cause of poor rolling is most often worn or overtightened wheel bearings during replacement. The lack of lubrication in them (it dries out over time) also increases rolling resistance. Again, under-inflated tires make the car roll worse. In the summer on winter tires and brakes jammed - the same thing. As a result: the worse the roll, the higher the fuel consumption.
Reason 17. Clutch wear
As the clutch discs wear, the lack of friction is compensated by a simple mechanism. However, when wear reaches a critical level, the clutch begins to slip. Accordingly, part of the energy generated by the engine is wasted. And fuel consumption is rising.
There are three ways to determine increased wear on clutch discs. First, the characteristic smell. When the clutch often slips under load, a sharp smell appears due to overheating of the discs, which over time is felt even in the car interior. Secondly, wear and tear can be felt if there is some experience in driving a particular car. When you press the gas, the acceleration and responsiveness of the engine decreases. That is, the momentum is gaining normally, but there is no intensive acceleration. The third way to determine critical disc wear is to disassemble and inspect the clutch mechanism.
Reason 18. Driving mode
Do not forget also that the fuel consumption indicators depend very much on the driving mode. So, when driving along the highway at the optimum speed in the highest gear, with a minimum number of accelerations and decelerations, the consumption is one. In the so-called urban mode, where the road sections are short, there is nowhere to accelerate, there are a lot of traffic lights and so on - more fuel is consumed. For example, if on the highway your car “eats” 7 liters per 100 km, then in the urban cycle the consumption will be at least 10 liters per 100 km. There is also the concept of mixed mode, when part of the path runs along the highway, and part in the city or over rough terrain.
Reason 19. Road surface condition
It is foolish to rely on the fuel consumption indicators indicated in the technical specifications if the car drives mainly on our famous bad roads. The figures, even with other ideal factors, will be noticeably overestimated. And all because a bad road means additional braking and acceleration, maneuvers, as well as long distances.
Winter with its ice is also related to this reason. When the roads are slippery, some of the energy generated by the engine is wasted uselessly on wheel spin. This should also be taken into account if you decide to ask yourself why fuel consumption has increased.
Reason 20. Weather conditions
The last reason, which should not be forgotten when measuring and accounting for fuel consumption indicators. The weather has a big impact on how a car rolls down the road. For example, if you drive with a headwind, the consumption increases by 5-10%. When driving on a wet road in the rain - about the same. In addition, with many weather factors, the driver is forced to turn on headlights, fog lights, a stove, air conditioning, and also adhere to a speed mode that is not the most favorable. Hence the increased fuel consumption.
There are many reasons for increased fuel consumption. Among them there are those that the car owner cannot influence in any way. This includes driving mode, weather conditions, road surface conditions, payload and others. Problems begin when the cause of increased fuel consumption is the deterioration of the car or its improper operation.