Gasoline 95 vs 98: Is the price difference worth it?

The octane rating, also known as RON (Research Octane Number), measures a gasoline's resistance to auto-ignition, i.e., knocking. Gasoline with a higher octane rating is more resistant to spontaneous combustion under pressure, which is crucial for modern engines, especially those with turbochargers and high compression ratios.

Practically, when the engine compresses the air-fuel mixture before ignition controlled by the spark plug, gasoline with too low an octane rating might ignite on its own, uncontrollably, a phenomenon called knocking or “valve rattle”. This can cause significant long-term damage to the engine, reducing efficiency and power. Therefore, it is vital to follow the manufacturer's recommendation.

The fundamental difference between 95 and 98 octane gasoline lies, as mentioned, in their resistance to knocking. 98 octane gasoline, due to its chemical composition and included additives, can withstand higher pressures and temperatures in the cylinders before auto-igniting, compared to 95 octane gasoline.

In addition to this superior knock resistance, 98 octane gasoline (or other premium high-octane variants like 100) often contains enhanced additive packages. These additives are designed to clean engine deposits, protect the fuel system, and theoretically improve combustion efficiency. However, the actual benefits strictly depend on your car's engine design.

Contrary to a popular perception, fueling with 98 octane gasoline will not automatically make your car more powerful or fuel-efficient, especially if the engine is designed to run optimally on 95 octane gasoline. Modern engines are equipped with knock sensors that automatically adjust the ignition timing based on fuel quality. If you use 98 octane in a 95 octane engine, the electronic system will detect an octane rating higher than necessary and, most likely, will not make any significant adjustments, as the engine is not optimized to exploit that extra knock resistance.

The only scenario where you might notice an increase in performance or a slight reduction in fuel consumption is if your car is explicitly designed for high-octane gasoline (e.g., 98 or 100) and you previously fueled with 95 octane gasoline. In this case, switching to the recommended fuel would restore the engine to its optimal operating parameters. Otherwise, for a full tank of 95 octane gasoline costing an average of 506 lei, the additional investment in premium fuel would, in most cases, be an unnecessary expense.

Filling up with 98 octane gasoline is truly necessary and justified only when the vehicle manufacturer explicitly specifies it. This generally applies to high-performance, sports engines, or those with turbochargers and very high compression ratios. These engines are calibrated to operate at optimal parameters, exploiting the superior knock resistance of high-octane gasoline.

Always check your car's manual or the inscription on the fuel tank cap. If it clearly states "minimum 98 RON" or an equivalent, then you should not compromise. Using a lower octane fuel could lead to knocking, power loss, and, in the long run, premature wear of engine components. For most common cars on our roads, for which 95 octane gasoline is sufficient, there is no real benefit that justifies the price difference.

According to updated data from the PretCarburant.ro platform, a 50-liter tank of 95 octane gasoline costs an average of 506 lei. This calculation is based on the national average price of 10.12 lei/L for standard gasoline, valid for the 1372 stations that have valid prices in our catalog.

It is important to note that prices can vary significantly between stations and localities. For example, we observed a spread of 0.11 lei/L between the minimum and maximum price for 95 octane gasoline nationwide. This difference, although it may seem small per liter, can translate into considerable savings over the course of a year, especially for drivers who cover long distances.

The safest and most correct method to find out what type of gasoline is suitable for your engine is to consult your car's user manual. There, the manufacturer specifies exactly the minimum recommended octane rating. This is the information you should always rely on.

Another readily available source of information is the sticker or inscription on the fuel tank cap. Many vehicles have a clear indicator showing whether you should use 95, 98, or even 100 octane gasoline. These indications are the result of engine tests and technical specifications, ensuring that fueling with the correct fuel will maintain the vehicle's performance and longevity.

Using 95 octane gasoline in an engine designed to run on 98 octane or higher presents serious risks. The main danger is uncontrolled detonation, meaning the air-fuel mixture ignites before the spark plug fires. The car's knock sensors will detect this and try to compensate by adjusting the ignition timing.

These adjustments lead to a significant reduction in engine power and efficiency. In the long run, repeated detonations can cause severe internal damage, such as melted pistons, damaged valves, or a blown head gasket, leading to costly repairs. Therefore, for an engine that requires 98 octane, it's not worth the risk to save a few lei per liter, especially when a 50 L tank of 95 octane gasoline costs, on average, 506 lei, while the 98 octane version, though we don't have a specific average, is always more expensive.

For an engine designed to run on 95 octane gasoline, using 98 octane gasoline does not offer significant long-term benefits for engine health. The main advantage of premium fuels lies in their more complex additive packages, which might help keep the fuel system clean and reduce carbon deposits. However, 95 octane gasoline available at stations in Romania also contains essential additives for engine protection.

If your engine does not specifically require a high octane rating, investing in more expensive gasoline will not translate into a longer lifespan or healthier engine operation. The money saved by fueling with 95 octane gasoline (which has an average price of 10.12 lei/L) could be more effectively directed towards regular maintenance, timely oil and filter changes, which are much more important factors for engine longevity.

Whether your car requires 95 octane gasoline, 98 octane gasoline, or even diesel or LPG, the best way to find advantageous prices is to use a price monitoring platform like PretCarburant.ro. We collect data from 1709 physical stations in Romania, with valid prices from 1372 of them, totaling 5577 prices updated daily.

You can check real-time prices for your area and quickly identify stations offering the best deals. For example, we observed today that the average price for diesel is 10.90 lei/L, while LPG is considerably cheaper, with a difference of 5.41 lei/L compared to gasoline. By using our map, you can save considerable amounts throughout the year, ensuring you don't pay more than necessary for fuel.