Regarding the mandatory transition to E10 gasoline with up to a ten percent share of the biocomponent, many motorists began to consider whether this objectively inferior gasoline bothers their car and what to do to overcome the negative properties of bioliquor (water binding, poorer stability, corrosiveness, lower calorific value, high mixing ratio) eliminate or at least reduce.

It has already been written many times that it is necessary to refuel with premium hundred-octane gasoline, because they do not contain bio-alcohol, or rather they use a chemically modified ETBE substitute, which does not have similar negative properties. However, you can also find a substitute for the bio component in some regular gasolines.

We will not deal here with complex physical and chemical equations and rather look at experience and knowledge from practice. On the Internet or in specialist publications, you can find more detailed information about what gasoline contains, what the octane number is and how it is measured. But you probably don’t need to know these details for normal car operation.

Cleans the engine and makes it last longer, but does not increase performance

The basic chemical composition of gasoline with a higher octane number is practically no different from standard gasoline, so pouring it into a car set to ninety-five hundred octane has about the same effect as convincing someone who has been drinking domesticated wine all his life that fifteen-year-old Glenlivet is a better drink. He kicks it into himself and achieves the desired effect, i.e. merging under the image, anyway.

Foto: Shutterstock / Bear Gong

If nothing else, additive gasolines (i.e. most high-octane fuels in our country) clean the engine of carbon deposits. But you can achieve the same effect by using your own cleaning additives in ordinary gasoline, which is usually a cheaper way.

So the Fabia 1.4 MPI ten-octane will not help with higher performance. This engine is set up to burn 95. You would have to play with the control unit and possibly increase the compression, which is no longer a meaningful modification for an ordinary car. In the case of engines tuned to regular gasoline, the desired effect of increased performance will not be achieved. Rather, on the contrary, if the engine is set to a higher octane number, the drop in performance when refueling with “worse” gasoline will be known as the control unit adjusts the advance and reduces, for example, the filling pressure of the turbocharger.

So high-octane gasoline won’t improve consumption and performance? That depends on what you mean by that. You can’t expect a car that when new had 100 horses and ran at 7 liters per 100 km to suddenly have 120 horses and go for six. Consumption will rather be helped by the fact that running on higher-quality gasoline cleans the injectors, the combustion chamber and, in cars with indirect injection, the valves and intake ducts, so the engine then works more efficiently. It takes in more air and atomizes the fuel better.

However, it is necessary to use high-quality additive gasoline (additive with cleaning additives and not necessarily high-octane) for a long time to show the effect. However, do not expect a miraculous increase in performance and consumption, rather you can only return the values ​​to where they were “new” when the engine was not yet clogged with carbon. So, going back to the above example, you’ll only get the power back to that 100 horsepower and the consumption will drop back down to seven liters, rather than the original values ​​miraculously improving.

But it will be known for some engines

In short, it mostly depends on what type of gasoline the car was developed for. If ninety-eight is prescribed, you should not fill the car with worse gasoline at all, because the engine could be destroyed by knocking. In more modern cars with advanced electronic control and knock detection, the control unit will already adjust the ignition advance and enrich the mixture a little (and possibly reduce the boost pressure), so the engine will not knock, but this will usually reduce power and increase consumption. A mixture that is too rich can also have other negative effects, for example it can endanger the catalyst and you will not easily pass the emission measurement (due to the too high content of hydrocarbons).

Photo: Dalibor Žák

Exact performance values ​​can only be verified in cylinder test facilities and you will never achieve repeatable results anyway. Even with the same gasoline, one day you measure, for example, 140 horses, and the next day five horses less or more. Engine performance is influenced by many factors, and it’s not just about gasoline.

But if the car is supposed to be 95, then gasoline with a higher octane number may not necessarily help. It depends on the design of the engine and perhaps also on whether the turbocharged engine has a sufficiently efficient compressed air intercooler. The air “stuffed” into the engine by the turbocharger (or mechanical compressor) must be cooled, thereby increasing its volume. The cooler the air you draw in, the more fuel the engine can burn efficiently. Thus, the 0.9 TCE and 1.0 TCE units in Renaults and Dacias are special, in which the change is noticeable when switching to gasoline with a higher octane number. It just drives better in certain driving situations.

However, a similar phenomenon can also be registered with some other modern turbocharged engines (it was also felt in some Škoda cars with the 1.2 TSI EA 111 engine), when during a long-term demand for high performance, the compressed air does not have time to cool and the engine performance drops noticeably (the most noticeable on a highway climb). In all of these cases, higher octane gasoline can help because it delays knocking and keeps the car running at full power for longer. The control units of turbocharged engines are also looking for an optimal band to which they can push the advance, so in theory the performance can be increased a little on better gasoline.

Photo: Dalibor Žák

When we once had the power of a used Octavia 1.4 TSI measured, it showed 7 kW more on the brake than what the manufacturer states. And that with a mileage of 209,000 km. At the time, we had Verva 100 in the tank. However, with modern turbo engines, measuring a higher value against the given parameters is not unusual even when using ordinary fuel, which was confirmed to us several times by colleagues from the industry who regularly verify the tested cars in the cylinder testing room.

With modern turbo engines with direct injection, you can kill two birds with one stone with high-octane gasoline. Firstly, the content of cleaning additives in premium fuel helps to keep the injectors clean (so they spray the mixture better and the engine simply works better) and the combustion chamber. And secondly, it’s possible that in certain driving situations, especially when high power is required for a longer period of time, higher octane gasoline may actually help. However, we are talking about such low values ​​that it is more than possible that the driver will even recognize it in normal traffic.

For most driving situations, when the engine is not working at full capacity, the benefit of a higher octane number will not be noticeable at all. Changes in fuel consumption are also debatable, as people often report that the car suddenly shows lower consumption values. This would need to be verified by long-term and accurate measurements.

Do you have a sports car? Do not refuel anything else

The vast majority of sports cars with modified engines require gasoline with an octane number of at least 98. The manufacturers state that gasoline with a lower octane number is fine, but in the owner’s manuals you will read that there will be a reduction in performance or that you should not demand maximum power from the engine.

Photo: Dalibor Žák

Sports cars can run on ordinary gasoline, but often at the cost of reduced performance and other restrictions (for example, manufacturers recommend not revving the engine above a certain limit and not demanding full power). But if you only drive a few thousand kilometers a year with such a car, you don’t have to worry about gasoline prices at all and just put the best that is sold in there.

All BMWs from the M division, practically all sports Porsches, but also a lot of sports cars with supercharged engines (Subaru WRX STI, Volkswagen Golf R, Mercedes A45 AMG and others) have a prescribed minimum of 98. Although they will work if you fill up with “worse” gasoline, they are not suitable for long-term operation or if you want full performance from such a car. So 95 won’t be a problem for a leisurely move on the highway, but before driving on the circuit, top up with a “hundred”.

Photo: Radek Chlud

Sports cars with turbocharged engines need high-octane gasoline. And if the car is professionally modified for competition, often even a hundred octane is the necessary minimum for maximum performance. The owners even use special additives to additionally increase the octane number (to 102 or even more). Custom cars with an adjustable control unit sometimes have the option to manually adjust the fuel map so that the engine runs on worse gasoline, but at the cost of reduced power. But you don’t have to deal with this at all with ordinary cars. And if you race with, for example, a modified Subaru WRX STI, you already know and have studied all this for a long time.

Saving gas on a high-performance sports car is nonsense anyway. Will you leave the brakes and tires on the track in the afternoon and wonder if you saved three crowns per liter of gasoline?

Some ordinary cars may need it

Higher octane gasoline was required for some of the Volkswagen Group’s older FSI engines (for example, the Octavia II with 1.6 FSI and 2.0 FSI engines). The Octavia RS 2.0 TFSI with the BWA engine needed 98, but the engine with the CCZA code will do with 95. The 1.8 TSI BZB unit must also have at least 98, gasoline with an octane number of 95 was sufficient for the CDAA and CDAB versions. The automaker even modified some civilian versions to make it possible to drive at 95.

At one time, high-octane gasoline was recommended, for example, for the three-cylinder 1.2 PureTec, but only as a precautionary measure due to the content of additives (and not all 1998s have them). Ninety-five remained in the technical regulation.

Photo: Dalibor Žák

You can usually find the recommended or at least the minimum value of the octane number for your car on the tank cap. You won’t do anything wrong with gasoline with a higher octane number, but don’t expect a sudden, miraculous improvement in engine parameters.

The basic data is usually indicated on the tank cap, where there is a round target with the value of the octane number, or the range. In addition to the octane number given by us according to the RON (Research Octane Number) methodology, you can also find AKI (Anti-Knock Index) or (R+M)/2 or PON (Pump Octane Number) values, especially for cars from Asian and North American market. Exceptionally, the MON (Motor Octane Number) value also appears.

In Europe, RON 95 corresponds approximately to the American AKI or (R+M)/2 value of 91. “American” 93 is “our” 98, and AKI values ​​94 to 95 correspond approximately to RON 100 gasoline. The most common AKI 85 gasoline is something like ” ours” Natural 91. Cars intended for multiple markets tend to have both RON and AKI values ​​listed together. And the range, or minimum value that can be refueled, is also often stated.

Do you drive a little? I prefer a hundred (or your own additives)

For regular cars that don’t have a sports engine, a higher octane rating isn’t usually necessary, but high-octane, bio-reduced gasoline will help if you don’t use the car for long periods of time. This is mainly known to motorcyclists, but it also applies to garden equipment, which often rests in winter.

Photo: Jan Majurník

Veteran owners have completely different concerns, such as where to get lead replacement additive. But they also have to somehow deal with the negative properties of the bio-component in gasoline. Stooktan is a waste for them, but at least such gasoline is more stable and less harmful to older vehicles.

Gasolines without a bio component or fuel containing ETBE instead of regular bio-alcohol do not bind water as much, are more stable and are more suitable for long-term storage. Nevertheless, it is better to use an additional additive for long-term shutdown, which serves specifically to stabilize the fuel for long-term storage. If you don’t want to deal with the additional mixing of additives, simply fill up with 100 with additives or any regular gasoline that you know does not contain a harmful bio component before a longer stoppage.

So, if we go back to the beginning, high-octane gasoline does not automatically guarantee higher performance and lower consumption, but due to the absence of bio-alcohol, it is more stable, suitable for long-term storage, does not harm older cars as much and, above all, thanks to the addition of special cleaning additives, it helps to keep the fuel system and combustion chamber clean . So the engine will simply work a little better. Performance and consumption may thus improve slightly, but rather only to the original values.