Is super unleaded worth the extra cost?
Super unleaded (sold as Shell V-Power, BP Ultimate, Esso Synergy Supreme+ and others) typically costs around 17p more per litre than standard 95 RON petrol. For certain vehicles it delivers real benefits. For most ordinary cars, the extra spend disappears into marketing rather than your fuel economy.
What RON actually means
RON (Research Octane Number) measures a fuel's resistance to premature ignition ("knock") inside the engine cylinder. When an engine knocks, the fuel-air mixture ignites before the piston reaches the right position, creating a characteristic metallic tapping sound and reducing efficiency. Higher RON fuel is more resistant to knock, allowing engines designed for it to run at higher compression ratios for better performance and efficiency.
Standard UK petrol is 95 RON (E10). Super unleaded is typically 97–99 RON. Premium products like Shell V-Power 99 hit 99 RON.
Cars that genuinely benefit
Modern high-performance and turbocharged engines are specifically calibrated for 97+ RON fuel. Many sports cars, premium German models (BMW, Mercedes-AMG, Audi RS) and performance variants specify 98 RON as the recommended minimum. In these cars, using standard 95 RON fuel causes the engine management system to retard ignition timing to prevent knock, which reduces both power and fuel economy. Running on super unleaded genuinely recovers that lost performance and efficiency.
- High-performance engines: BMW M, Mercedes-AMG, Audi RS, Porsche. 97+ RON recommended, real gains from super.
- High-compression turbocharged engines: many modern performance variants of family cars. Check your handbook for the recommended minimum RON.
- Track use: on track with sustained high loads, premium fuel can noticeably improve power and reduce the risk of knock.
Cars that don't benefit much
Most standard petrol cars (a Ford Focus, a VW Golf, a Toyota Corolla) are engineered and calibrated for 95 RON. They have knock sensors that can adapt to different fuels, but there's no performance headroom to unlock with higher octane. The engine is already running at its designed optimum. Studies consistently show that standard family cars see fuel economy improvements of under 1% when switched to super unleaded, far less than the ~10% price premium.
Premium fuel advertising often implies that "cleaning additives" will benefit any engine. While additives can help maintain injector cleanliness over time, the benefit is marginal for most modern cars with clean fuel systems. It's not zero, but it's not worth 17p per litre either.
Super unleaded and E10 compatibility
An important point often overlooked: super unleaded is E5 fuel (5% ethanol), not E10. This makes it the correct choice for vehicles incompatible with E10: older cars, classic vehicles, and some motorcycles. For those drivers, the extra cost is the cost of using the right fuel, not a premium for performance.
Check your car's handbook. If it specifies 97+ RON, use super unleaded. You'll get your money's worth. If it says 95 RON, stick with standard petrol and spend the saving somewhere else.