Octane

What happens if I use the wrong octane petrol in my vehicle?

Different vehicle models have different octane requirements. Using a petrol octane grade higher than that required by your vehicle is unnecessary and a waste of money, particularly since no added benefits to engine performance or efficiency will be achieved. Using petrol with too low an octane may decrease engine performance and fuel efficiency, and may cause the engine to knock which can cause engine damage over time. It should be noted that the octane requirement of a specific vehicle is dependent on many variables, including operating conditions and the way it is driven, with octane requirement peaking under high load, wide-open-throttle conditions.

For more information please use the following Engen sources:

Customer Call Centre: 08600 36436

Technical Advice
Tel: 0860036436 press 3
Email: 1call@engenoil.com

Retail Station Forecourts:
Please ask the forecourt manager to assist in accessing the vehicle compatibility database information.

Why should I not use an octane grade that is higher than my car actually requires?

There will be no additional benefit to driveability or performance of your vehicle if you use a higher grade than it requires.

Petrol with a higher octane requires more severe refining and greater energy use in the production process. If not offset by greater fuel efficiency of the vehicle using the fuel, this extra energy use is wasted energy. This wastage results in higher emissions of greenhouse gas (carbon dioxide), which harm our environment.

The use of octane grades higher than your vehicle actually requires will cost you more, cost the country more and have a negative environmental impact.

What is the impact of octane on fuel consumption?

Where a vehicle is fully satisfied by 93 octane, in the sense that it delivers optimal performance and fuel economy on that grade, using a higher octane than 93 will not result in any improvement in performance or fuel economy, neither will it result in a decrease, but using the higher octane is unnecessary and inherently wasteful. This will apply to the great majority of vehicles inland, which are satisfied by 93 octane.

If a vehicle is designed to operate at the coast on 95 octane, but has an engine management system with a knock sensor, it will enable the vehicle to operate without damage on lower octane fuel, typically down to 91 octane. The way this works is that as soon as the knock sensor detects incipient knock, it retards the timing to prevent this. Damage to the engine is thereby prevented. However, any adjustment of the spark timing from the optimum position will impact on efficiency and hence fuel economy (and power). This is where a trade-off may come into effect, between efficiency and performance on the one hand and fuel price on the other.

Vehicles exhibit their maximum octane requirement under high speed/ high load conditions. Thus when operating under light load (and avoiding excessive acceleration etc.) one can often use a lower octane fuel without any fuel economy penalty. Driving habits can have a significant impact. Thus it will make sense for motorists to try different octane grades (provided that these are indicated by the manufacturers as being compatible with their cars) to make their own trade-off where this is applicable. Obviously the price differential between grades is a relevant factor in doing so.