Is it cheaper to refuel in the morning than at noon? Is the oil label directly proportional to the oil quality? Car exhaust pipe displacement becomes more, is the oil added bad? ...... Take stock of the "refueling" misunderstandings in life.
Every winter, the problem of short endurance and false mileage of electric vehicles makes the majority of new energy car owners headaches, and traditional fuel vehicles show great advantages in endurance. The most closely related to the endurance of fuel vehicles is to refuel gasoline, after all, it cannot be driven without fuel. But a lot of common sense related to refueling is actually a rumor, and even let many old drivers be recruited.
Myth: Is it cheaper to refuel in the morning?
Truth: There is little difference between early, middle and late
There is always a saying among old drivers: "It is most cost-effective to refuel in the morning or at night, especially in the morning, and spending the same money can add more fuel." ”
Such a statement is not a vacuum, according to the principle of thermal expansion and contraction in physics: the lower the temperature of the liquid, the higher the density; the higher the temperature, the lower the density of the liquid. Gasoline refueling is billed according to volume rather than weight, and at the same volume, the higher the density, the greater the mass, and at the same price, the more oil is added.
Because of the "endorsement" of scientific principles, many car owners believe in this, and some people really go to refuel early in the morning. But the end result is not difficult to think of, and the purpose of saving money has not been achieved. Don't scientific principles apply anymore? This is not the case.
Guo Qun, a professor-level senior engineer of the Sinopec Science and Technology Development Department, explained that at present, gas stations have built underground oil storage depots, and they all have a certain degree of protective layer, gasoline is stored at a constant temperature all year round, and will not be affected by the external temperature, and the statement that refueling sooner or later saves money will naturally not be established.
"Even if the technical level in the early years did not meet the current standards, it was impossible to achieve underground constant temperature oil storage, and the density of gasoline under different temperature conditions did not change much, and the price difference was very small."
In fact, if the claim that refueling in the morning is more economical is really true, and refueling in winter should be more economical than in summer, then the price of oil should change throughout the year, otherwise gas stations will only lose money. Therefore, a good way to really save fuel is to develop good driving habits, and we tend to use more fuel in our daily cars because of queuing, idling or violent driving.
▲ November 19, 2021, Nanjing, the staff of a gas station refueled vehicles
Myth: The higher the oil label, the better?
Truth: Oil labeling and quality are not directly related
The main components of gasoline are C5-C12 aliphatic hydrocarbons and naphthanes, as well as a certain amount of aromatic hydrocarbons, as a kind of petroleum refined products, gasoline has a high octane number, that is, anti-knock combustion performance.
According to China's current laws and regulations, gasoline is produced and sold according to the brand, the brand is divided according to the octane number, and there are 3 gasoline brands in The country (IV), which are No. 90, No. 93 and No. 97. The countries (V) are No. 89, No. 92, No. 95 and No. 98 respectively. The higher the grade, the better the explosion resistance.
Since the price of No. 95 gasoline is higher than that of No. 92 gasoline, coupled with the relatively high price of intermediate family cars, No. 95 gasoline is generally added, many car owners therefore believe that the higher the oil label, the better? Some people even deliberately add high-grade gasoline in order to improve the quality of combustion.
In this regard, Guo Qun said that the label of gasoline is related to the ability to resist explosion, but it is not directly related to quality. This is because most civilian gasoline engines use the four states of "suction - compression - combustion - exhaust" to work repeatedly, and the specific need to fill what kind of oil, mainly lies in the "compression ratio" parameter.
The compression ratio refers to the ratio of the cylinder volume of the piston at the lower stop point of the stroke to the upper stop point. Cars with a high engine compression ratio have better dynamics and higher thermal efficiency, and the acceleration and maximum speed of the vehicle will be increased accordingly. Therefore, many mid-level cars use high compression ratio engines and need to be filled with high-grade gasoline. Compact cars and small cars use low compression ratio engines and fill low-grade gasoline with fuel economy.
Guo Qun suggested that consumers do not need to deliberately add high-grade gasoline, but should refuel according to the label given by the manufacturer, and can also be judged according to the compression ratio of the engine. For example, the compression ratio of about 8.0-8.5 can choose 92-95 gasoline, the compression ratio of 8.5-9.0 can choose 95 gasoline, the compression ratio of 9.5-10.0 can choose 95-98 gasoline, and the compression ratio is higher than 10.0, it is recommended that 98 is better.
Rumor: Can adding "fuel treasure" reduce fuel consumption?
Truth: The real role is exaggerated, and it is more important to maintain it on time
"Your engine is all carbon deposited, add a bottle of fuel treasure, right?" In recent years, when many car owners go to gas stations to refuel, they are always enthusiastically promoted by the staff to promote a fuel additive that can improve combustion efficiency and remove carbon deposits - fuel treasure.
Although it is not large, but the price is not cheap, generally 6 bottles a group of about 200 yuan, or even higher. There are also car owners who feel that the effect is not obvious after the addition, and directly call to pay the IQ tax.
Guo Qun said that there are two kinds of fuel treasure on the market at present, one claims that it can adjust the octane number, improve the thermal efficiency of the engine, and improve the driving experience.
Another kind of fuel treasure is a cleaner for engine carbon deposition, which peels off the carbon deposit inside the engine and discharges it after high temperature combustion, which plays a certain role in dissolving and removing carbon deposits.
"It is worth noting that how much carbon deposition can be removed by this additive, the current scientific community does not have accurate evaluation values, and it is impossible to evaluate the real effect." Guo Qun said that on the other hand, the fuel treasure is mixed in gasoline, only the position where gasoline can reach can produce a cleaning effect, and the position where gasoline cannot reach, there is theoretically no possibility of cleaning, such as throttle valve, direct injection engine intake valve back will have carbon deposition.
Therefore, the real effect of fuel treasure is exaggerated, and it is not as "magical" as advertising or refueling workers say.
Consumers should be more cautious when choosing products, the most effective way to remove carbon deposits, or to the 4S store or regular auto repair shop on time for vehicle maintenance and maintenance, maintenance union with professional equipment for users to clean up, safe and efficient, targeted is also better.
Rumor: The exhaust pipe displacement is more because the oil quality is not good?
Truth: After gasoline is burned, water vapor becomes cold and becomes water
With the advent of winter, the temperature continues to drop, and many car owners have observed this phenomenon, that is, the exhaust pipe of the car will drip outward, and even continue to "flow water". This has surprised many car owners, thinking that it is caused by adding inferior gasoline.
When gasoline is completely burned, water and carbon dioxide are generated, and water becomes water vapor at high temperatures, but when the temperature is lower than 100 ° C, the water vapor condenses into water. If the condensed water droplets accumulate, they become liquid water, which reaches a certain amount and is discharged through the exhaust pipe. So we see that the water in the exhaust pipe is actually the result of the condensation of the water vapor generated after the combustion of gasoline in the exhaust pipe and silencer.
It is worth mentioning that the exhaust pipe of the car generally has a small hole for drainage, and the lower the temperature, the more obvious the phenomenon of running water. Guo Qun said that in the northeast region of China, when vehicles wait for red lights in winter, they can often see the phenomenon of a group of cars collectively "draining". This phenomenon is not a problem with the oil product of the refueling, nor is it a failure of the fuel system, but it shows that the engine is fully burned and the working conditions are good.
But it should be noted that if the liquid in the exhaust pipe is black, and very sticky, but also accompanied by blue smoke, the oil consumption is very fast, the engine power is obviously insufficient, etc., this situation indicates that the engine's piston, cylinder liner, piston ring clearance is too large, can not work properly, should be immediately professional inspection and maintenance.
Rumor: Private gas stations are all "black heart oil"?
Truth: The source of oil products is guaranteed, but the "big factory" is more trustworthy
China's gas stations are composed of three parts: state-owned, private and joint venture. By the end of 2020, among the 112,000 gas stations in the country, 50% of the gas stations operated by state-owned enterprises, 48.1% operated by private enterprises, and 1.9% by foreign-funded enterprises.
In the private gas stations, in addition to Sinochem Petroleum, Yanchang Petroleum and other well-known oil companies, there are also many township names or random name of the "private gas stations", compared to the state-run gas stations, private gas stations the price is low, the anecdotes have also been circulating "private gas station oil quality is poor" "rural small gas stations are black heart oil" saying.
"China's "Technical Specifications for the Management of Refined Oil Retail Enterprises" clearly stipulates that refined oil retail enterprises should have stable and legal supply channels for refined oil products, and should purchase refined oil products from enterprises with refined oil wholesale business qualifications." Guo Qun said that from the legal point of view, the source of oil from private gas stations and state-run gas stations is guaranteed, and there is no "black heart oil" in theory.
However, Guo Qun also reminded consumers that a very small number of unreliable small gas stations, or private gas stations in remote areas, due to insufficient strict supervision, do not rule out the possibility of using inferior oil. The so-called "black gas station" has not disappeared, if it is not a particularly urgent situation, it is still recommended to give priority to the choice of sinopec, PetroChina and other state-run gas stations, or well-known private gas stations, after all, "big factories" are more trustworthy.
Interview experts
Guo Qun (Professor-level Senior Engineer, Department of Science and Technology Development, Sinopec)