RON95 vs RON97: Does higher-octane fuel really make your car better?

At Malaysian petrol stations, drivers generally have two main choices at the pump: RON95 or RON97.

Because RON97 costs more, there are plenty of claims about whether it is worth the extra money. Some say it gives better fuel economy, while others believe running RON97 regularly is better for the engine.

But is RON97 really better than RON95 across the board?

From an engine-design and fuel perspective, the answer depends on what your engine was designed to use.

What does RON actually mean?

RON (Research Octane Number) measures how resistant petrol is to knocking. It does not indicate how clean the fuel is or how much energy it contains.

The higher the octane rating, the better the fuel can resist pre-ignition or uncontrolled combustion when exposed to high temperatures and pressures inside the cylinder.

In terms of basic chemical composition, RON95 and RON97 do not have a huge difference in energy density. In other words, moving from RON95 to RON97 does not automatically mean the fuel contains significantly more energy.

Will RON97 give you more power or better fuel economy?

For most naturally aspirated engines in everyday cars — including common sedans and SUVs — the engine is designed around a relatively modest compression ratio, while the ECU is calibrated to run properly on RON95.

If your car only requires RON95, filling it with RON97 does not automatically give you more horsepower or better mileage. The engine simply may not be able to make use of the extra knock resistance.

Think of it this way: putting professional running shoes on an average runner does not automatically make them faster.

The situation is different for higher-performance and turbocharged engines.

Luxury cars, performance models and some high-boost turbo engines may specifically recommend or require RON97, RON98 or another high-octane fuel in the owner's manual.

These engines operate at higher temperatures and compression pressures. If the fuel's octane rating is too low, the engine may retard ignition timing to prevent knocking. That can reduce performance and, depending on the conditions, increase fuel consumption.

When does RON97 make sense?

When the manufacturer recommends it: Check the fuel label inside the filler flap or the owner's manual. If the manufacturer specifies RON97, that is the fuel you should use.

For heavy loads and long-distance driving: If you regularly drive long distances, climb steep roads or carry heavy loads — for example, frequent trips to Genting Highlands or Cameron Highlands — higher-octane fuel can provide greater resistance to knocking under high-load conditions.

The Verdict

RON97 is not automatically better than RON95. The more important question is which one suits your engine.

For a regular daily driver designed to run on RON95, there is little reason to pay extra for RON97 simply because it has a higher octane rating.

If you drive a turbocharged or high-performance car whose manufacturer recommends high-octane fuel, however, using RON97 can help the engine operate as intended and maintain its designed performance.

The simplest answer is also the most reliable one: check the fuel recommendation on the filler flap or in your owner's manual.