Gasoline is one of the few products of modern industry, the quality of which is strictly regulated by the state. Fuel cannot be produced according to secret specifications. A special branded composition with "exclusive ingredients" is not possible. Unfortunately, not all manufacturers and sellers comply with the regulations. As a result, the average consumer is forced to be aware of the signs of bad gasoline. Many people know them, and they perfectly distinguish high-quality fuel from low-quality fuel. This material on the ABS website is intended for those who want to learn how to independently determine which gas station has the best gasoline.

What kind of gasoline is good?

Any gasoline intended for refueling vehicles must be unleaded. Gas stations are not required by law to notify drivers of this. This is the default rule. If you buy gasoline, it is unleaded. At least it should be.

High-quality gasoline should not contain metal-containing additives. This includes lead, iron, manganese. With the naked eye, you can see the presence of only ferrocenes in the composition. They are also related to metal-containing additives.

The content of methanol in gasoline is strictly regulated. This substance adversely affects the resource of an automobile engine. If the methanol content is above the norm, then the spark plugs, lambda probe and catalyst quickly “die” (more on removing the catalyst on a car without a service station). For unscrupulous manufacturers, it is advantageous for its cheapness. It also very effectively increases the octane number. The abuse of methanol allows low-grade gasoline to be sold at an inflated price.

The maximum allowable content of the mentioned substances in high-quality gasoline:

  • lead — 2.5 mg/l;
  • iron - 0.01 mg/l;
  • manganese - 0.25 mg/l;
  • methanol - no more than 0.17% of the total volume.

By law, gasoline is allowed to be tinted. However, green and blue pigment cannot be used. Manufacturers do this in order to distinguish their products from other brands. Once upon a time, tinting was used to protect against counterfeiting. Today this task is not pursued.

Quality gasoline may contain additives. Permitted ones include antioxidant, anticorrosive, detergent and multifunctional. It is forbidden to use additives that have side effects on the car engine.

Good gasoline is clear, free of dirt and water.

There are other standards as well. But for the average driver, these are just abstruse terms that cannot be put into practice. But you can determine bad gasoline by indirect and direct signs. Here are 10 of them. This is enough to learn how to identify low-quality fuel without a laboratory, with bare hands.

Red color

The law allows the use of dyes. But reddish gasoline is a bad signal. This color is obtained due to cheap metal-containing additives that are used to increase the octane number. They have already been mentioned above. These are ferrocenes. For the driver, this is a real problem. Ferrocenes are deposited as permanent deposits on spark plugs, valves, and oxygen sensors.

It is almost impossible to see such a shade at a gas station. How to "calculate" ferrocenes at home is described below.


Many consider yellow to be the natural color of gasoline. If you pour a little high-quality gasoline into a transparent glass container, then under certain lighting conditions it can really have a slightly yellowish tint. But only slightly. If gasoline has a rich yellow color, this means that the manufacturer overdid it with monomethylamine. This component is used to make cheap additives that can increase the octane number.

Bad smell

Quite a subjective sign of bad gasoline. Many a priori do not tolerate the smell of fuel, and for them it all stinks. However, low-quality gasoline has a particularly unpleasant odor. An experienced driver can easily determine it “without a laboratory”. An unpleasant smell is felt both when refueling and when the car is running without a catalyst.

Engine doesn't start well

Gasoline is food for the car engine. As a person reacts to bad food, a car reacts to low-quality gasoline. The first symptom is that the engine does not start well. Especially when it's cold. If the engine does not start at all, the cause may not be only in gasoline. There is detailed material about this on the ABS website.

Engine idling erratically

Engine idle is a highly accurate indicator of bad gas. If the quality is even slightly worse than usual, this clearly affects the operation of the engine. In particular, it starts to work unstably, “trying” to stall, the speed fluctuates, vibrations are felt. The electronic control unit simply cannot "adjust" to bad gasoline. Such an algorithm is not registered in his memory. If the engine is carbureted, then idle speed cannot be adjusted.

Engine stalls

For the engine to work stably, gasoline must burn. If it contains water, dirt, cheap additives, it ignites once. This is especially evident in technology with single-cylinder engines.

Decreased vehicle dynamics

Of all the indirect signs of bad gasoline, this is the most obvious. Any driver who has been driving for more than a day knows perfectly well how the car reacts to the accelerator pedal. When low-quality gasoline gets into the tank, the car seems to be “held” by someone. He slowly accelerates. It jerks when you press the pedal hard. It may stall if you are a novice driver, and you are still not very good at shifting gears on a manual transmission. On cars with automatic transmission, dynamics problems also occur.

Increased fuel consumption

There is detailed material on fuel consumption on the ABS website.

To do the same job, you need much more bad gasoline than high-quality one. This is because the air-fuel mixture ignites with a delay, sluggishly, through time. The low calorific value of bad gasoline also affects this. As a result, in order to produce the same amount of energy, the electronics feeds a rich mixture into the cylinders, as the sensors “tell” it that it is poor.

Controlling fuel consumption is a good habit for any motorist. This is an indicator that can tell in a timely manner not only about the quality of gasoline. The consumption is also significantly affected by the technical condition of the car, driving skills and style, and a number of other factors that are devoted to entire articles on the Internet. You can control it in several ways - using the on-board computer, making control measurements, noting on the odometer how much the car has traveled since the last refueling, and so on.

There is also a separate article about this.


Detonation is when you hear a clicking sound when you press the accelerator pedal. In the engine at this time there are "unauthorized" explosions of the air-fuel mixture. Gasoline is not ignited by spark plugs. It explodes from the pressure that is created due to compression and compression ratio (more on the difference between these terms). Fuel burns out of time, releases its energy much faster than the engine is designed for.

In addition, self-ignition occurs before the piston has time to pass the top dead center. As a result, the released energy “presses” on it, creating resistance to the natural rotation of the crankshaft. The result - the power and torque are reduced, the car rides badly. Detonation will inevitably reduce the life of the engine.

The main cause of knocking is the low octane number. This characteristic directly indicates the resistance of the fuel to detonation. The higher the octane number, the higher the detonation resistance is also higher. If fuel with a low octane rating is poured at a gas station, this symptom appears.

No less problems when the octane number is raised by low-quality additives or gases like propane or methane. You will be honestly filled with 95th gasoline, which you can verify with a pocket octanometer (more on that below). However, the gases will quickly evaporate, leaving a supply of low-octane gasoline in your car's fuel tank. The worst thing is that the engine will run normally for quite some time after visiting the gas station, and then it will suddenly start to detonate.

The car often breaks down

Poor-quality gasoline affects the technical condition of the car, by analogy with the use of harmful products (or poisons in the form of alcohol, tobacco, drugs) by a person. First of all, the power supply and ignition system suffers. Spark plugs quickly “die”, filters, nozzles, lambda probes, catalysts become clogged, valves “burn”. If you drive on bad gasoline all the time, a lot of soot forms on the working surfaces of the engine. Over time, it flakes off and scratches the cylinders. As a result, compression is reduced.

If your car breaks down frequently, try changing gas stations. You may be running bad gas.

Filled with low-quality gasoline - what to do?

If the dynamics worsened or fuel consumption increased, and other symptoms of bad gasoline do not appear, this is not a problem. You don't have to do anything. Just use up low-quality gasoline, and next time change the gas station. In extreme cases, dilute bad gasoline with good.

If the engine does not start, stalls, twitches, "stinks", detonates - do not torment it. Stop. Drain low-quality gasoline (on your own or at a service station). Refuel a quality one. Do it. Even if you have to pay for the services of a tow truck. In any case, it will cost less than repairing the engine.

If low-octane gasoline is filled (the engine knocks), then the octane number can be increased independently directly in the fuel tank. For this, special additives are sold in automotive stores.

Please do not encourage unscrupulous fuel producers and sellers with your silence. Always keep your cash receipt. Filled up with bad gas? Do not be shy. Submit your claims to the head of the gas station. Call the company hotline. This is at least.

How to protect yourself from low-quality gasoline?

  • Do not buy suspiciously cheap gasoline. The low price does not mean that the manufacturer has reduced the cost of gasoline with innovations or simply decided to do charity work.
  • Don't fill up at double gas stations. These are gas stations that use a well-known brand, but have nothing to do with it.
  • Order and pay for gasoline carefully. Remember that there are several types of fuel with a similar name. Pay attention to the prefixes to the standard labeling - "plus", "premium", "eco" and so on. Be sure to ask what these prefixes stand for. Very often these are just letters that will not affect the dynamics of the car in any way, or vice versa, worsen it.
  • Refuel at trusted gas stations. Opinions about the same company are often radically different. Of course, it's worth listening to other people's opinions. But always draw conclusions based on your feelings.
  • Buy an octane meter. This is a quick octane rating tool. You can apply it directly at the gas station.
  • Periodically check the quality of gasoline. For example, the folk method. Apply a couple of drops of gasoline to a clean, white, dry cloth. Wait for the fuel to evaporate (a couple of minutes). If the napkin is clean, without stains, dirt, gasoline is not bad. If the napkin does not dry for a long time, then there is a possibility that there is water in the gasoline.

Video: bad gas in the car


There are direct and indirect signs of bad gasoline. Immediate signs - appear when studying color, transparency, purity, octane number. Indirect signs are the reaction of your car to low-quality gasoline. Did you send this one? Better drain. Greed and an attempt to save money in this case can result in serious sudden repair costs.