Octane Rating: Complete Guide for Gasoline in Romania

The octane rating is an indicator of gasoline's resistance to autoignition, meaning spontaneous and uncontrolled combustion before the spark plug fires. In simple terms, it measures how well a fuel can resist compression without prematurely detonating in the engine cylinders. A higher octane rating means increased resistance to this phenomenon, popularly known as „engine knocking” or „detonation.”

This aspect is crucial for the proper functioning of the engine, especially under high load or elevated temperatures. Standard gasoline available in Romania, which we find at an average price of 8.65 lei/L according to our monitoring, has an octane rating of 95, making it suitable for the vast majority of modern vehicles.

The numbers 95, 98 or 100 represent the octane rating of gasoline, indicating its resistance to detonation. Gasoline with an octane rating of 95 is the standard on the Romanian market and is recommended by most car manufacturers for their vehicles. It offers an optimal balance between performance and cost, with an average price today of 8.65 lei/L at the stations we monitor.

Gasolines with octane ratings of 98 or 100 are considered "premium" and have greater resistance to pre-ignition. They are formulated for high-performance engines, those with a high compression ratio or those equipped with turbochargers, which require more precise and controlled combustion. Although they often come with special cleaning additives, their main advantage is precisely this superior detonation resistance, which typically justifies their higher price compared to gasoline 95.

The importance of the octane rating for a car's engine is fundamental, as it ensures efficient and controlled combustion of fuel in the cylinders. Modern engines are designed with specific compression ratios, and if the gasoline used has an octane rating that is too low, it can self-ignite under pressure before the spark plug triggers the spark. This phenomenon, called detonation or „piston knocking”, generates shock waves that can long-term damage internal engine components, such as pistons, connecting rods, or valves.

On the other hand, if an engine is designed for 95 octane gasoline, as is the case for most cars in România, fueling it with 98 or 100 octane gasoline will not bring notable performance benefits. The engine's electronic system (ECU) will adapt to the type of fuel, but it will not be able to exploit the superior detonation resistance if it is not designed for a higher compression ratio. Thus, the difference of 0.66 lei/L that we can observe between the minimum and maximum price of 95 octane gasoline between stations can be more relevant for drivers' budgets than an unnecessary investment in premium fuel.

The use of higher octane gasoline, such as 98 or 100, is recommended in specific situations, primarily when the vehicle manufacturer explicitly indicates it in the owner's manual. This is often the case for sports cars, luxury models, vehicles with supercharged (turbo) engines, or those with very high compression ratios, which require superior detonation resistance to operate at optimal parameters and prevent damage.

Also, performance-modified cars that have been equipped with a "chip tuning" or other enhancements that increase cylinder pressure or ignition advance will benefit from higher octane fuel. In these cases, using 95 gasoline, which has an average price of 8.65 lei/L, could lead to a loss of power or, more seriously, accelerated engine wear. It is important to always follow the technical specifications to ensure the engine operates efficiently and safely, even if this means a higher cost for a 50-liter tank fill, which for 95 gasoline is 432 lei.

Contrary to a widespread perception, premium gasoline with an octane rating of 98 or 100 is not automatically better for every car. Most cars manufactured in recent years are designed and optimized to run perfectly on 95 octane gasoline, as also indicated in their user manuals. Fueling an engine designed for 95 with higher octane gasoline will not bring real benefits in terms of power, consumption, or durability, as the engine management system is not programmed to exploit this additional detonation resistance.

Practically, investing in more expensive fuel when the car doesn't need it is an unnecessary expense. 95 octane gasoline has an average price of 8.65 lei/L, and premium fuels are, naturally, more expensive. If your car runs flawlessly on 95 octane gasoline, there is no technical or economic reason to pay extra for a higher octane rating. The car's electronic system will adjust parameters anyway to avoid detonation, but it will not "gain" anything from that extra octane.

Additives present in premium gasolines can, indeed, influence engine performance and lifespan, but in a more subtle way than the octane rating itself. These additives are formulated to clean the fuel system, injectors, and valves, preventing carbon deposits. Effective cleaning can contribute to maintaining combustion efficiency and a longer lifespan for engine components, especially in direct injection engines, which are more prone to deposits on intake valves.

However, it is important to note that even standard gasoline, including that with an octane rating of 95, available at an average price of 8.65 lei/L, contains minimum additives required by law to ensure decent operation and protect the engine. The benefits of additives in premium fuels are more evident in older engines or those that have covered a high number of kilometers and may already have deposits. For a modern, well-maintained engine constantly fueled with quality fuels from the 1390 monitored stations, the impact of additional additives in premium gasoline might be marginal, not revolutionary.

The cost of a full tank of gasoline 95, approximately 50 liters, amounts today to around 432 lei, based on the average price of 8.65 lei/L that we have recorded. This amount is an important benchmark for drivers planning their car expenses budget. However, for a complete picture, it is useful to make a comparison with other types of fuel available on the Romanian market.

Diesel, for example, is consistently more expensive, with an average price of 9.44 lei/L, meaning that a full tank of 50 liters costs approximately 472 lei. On the other hand, auto LPG remains the most economical option, with an average price of 4.56 lei/L, representing a significant difference of 4.09 lei/L compared to gasoline. This major price difference per liter makes a full tank of LPG considerably more accessible, attracting many drivers towards car conversion. Prices fluctuate, of course, and it's worth checking them constantly.