Category: New cars

The Mystery Of Two Octans


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Video: The Mystery Of Two Octans
Video: OCTANS MODCAST #4 2023, February
The Mystery Of Two Octans
The Mystery Of Two Octans

In the “smoking room”, the opinions of colleagues were divided - some claimed that there was no difference in the behavior of the car, others insisted on the opposite. My friend warmed up interest - the owner of a new foreign car, often filling it with "ninety-fifth" (although fuel with a lower octane rating is written in the instruction manual). Like, the AI-95 is cleaner, and the car rides better. It became clear that only measurements at the training ground would judge the dispute.


In order for the tests to be correct, first make sure that the fuel matches the declared octane number. Therefore, gasoline purchased at a renowned gas station was sent for an independent examination. The experts reached a verdict: in the canister with the AI-92, one hundred percent “ninety-second” was poured, and the detonation resistance of the fuel from another tank was 94.9. A negligible shortfall of one tenth will not affect the purity of the experiment.

For testing, they chose VAZ 2110 3 - the plant obliges the owners of this model to refuel the AI-95, and the “ninety-second” is outlawed. However, not all follow the prescription - out of ten "one hundred and third", God forbid, the couple will be interested in high-octane fuel. However, more on that later.

The test program is standard - with the help of the Korsis measuring system we fix acceleration dynamics, maximum speed, elasticity of the car on AI-92 and AI-95 gasoline. In addition, we also compare fuel costs - for this we connect a fuel meter to the fuel line. The difference is easiest to catch in steady driving conditions - in fifth gear at speeds of 60, 90 and 120 km / h.



Judging by the results (see table of measurements), both skeptics and optimists turned out to be right. The best acceleration, elasticity and maximum speed "ten" showed on gasoline AI-95. The difference in performance is noticeable, although it can not be called significant. An additional 2.1 km / h of maximum speed can only be detected by an accurate measuring device, as well as 0.8 s when accelerating to hundreds. Probably, the driver will feel small changes in the behavior of the car - on the “ninety-fifth” VAZ 2110 3 rides a little smoother and more confident. It was not possible to catch the difference in gasoline consumption - hundredths of a liter, rather, the permissible measurement error.


Real indicators are not difficult to explain in terms of theory. Electronic engine management systems, including the test VAZ 2110 3, include a knock sensor that corrects the ignition timing. When the engine is running on AI-95 high-octane gasoline, the control unit increases the ignition timing, while changing the values ​​of many parameters that determine power and economic indicators. In other words, theoretically, on high-octane gasoline, consumption decreases slightly, power and torque increase.

In our case, high-octane gasoline added kilowatts and Newton meters, which influenced the dynamics of the VAZ 2110 3. It is likely that a car of some other brand will have a more noticeable difference in costs than in power indicators. In any case, only devices will be able to catch it - by eye, everything will be about the same!


VAZ 2110 3 eats on average about 8 liters of gasoline per 100 km. So, if you fill in the "ninety-fifth", then every thousand kilometers with the current difference in prices for AI-92 and AI-95 will cost 80 rubles more. With an average mileage of 20 thousand km per year, an extra 1600 rubles will dissolve in the tank. Regarding the total cost of fuel - little money. But the list of additional costs has not yet been exhausted.

Some motorists bluntly believe: the higher the octane number, the better the fuel. Long-term operation of editorial cars on different grades of gasoline proved that the AI-95 (the one that is offered at ordinary Russian gas stations) quickly disables spark plugs. On some machines they have to be replaced every 3-5 thousand km. This is confirmed by car repair specialists. Estimate the cost of parts and replacement work and decide whether the game is worth it … candles?

If the compression ratio in the cylinders is lower than 10.5, and the engine is equipped with fuel injection and ignition feedback (read, knock sensor) - it can be fed “ninety-second”. Nothing bad will happen - in any case, due to missing octane units. The ignition timing is adjusted over a fairly wide range, so that the unit painlessly digest gasoline with a low octane rating.

All editorial “dozens” with 8- and 16-valve engines departed from the life tests on AI-92 fuel. We preferred to lose the "traffic light race" (although this is still a question!) Than overpay for gasoline.

Russia is trying to be like Europe, where most cars are converted to high-octane fuel. Fine! But do not forget that the quality of European gasoline is much higher than the current Russian. Of course, the manufacturer's recommendations should be listened to. If only AI-95 is written in the operating manual, then at least during the warranty period it is better to comply with the factory requirement. Otherwise, the dealer will have a reason to deprive you of a guarantee. Next - think for yourself. The initial data and the algorithm for solving this problem are described above.

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