Is it worth paying more for SP98 petrol instead of 95?

All petrol on sale in France today is unleaded – sans plomb. The old leaded ‘super 97’ (equivalent to UK four-star) has been banned since 2000, though a version continued under the name for a few years with potassium replacing the lead. Owners of certain classic cars from the pre-unleaded era opt to make modifications to the engines or to use additives in the petrol.

The main kinds of petrol are SP95 or SP98, and the difference is the percentage of octane, one of the components of petrol.

SP95 is the standard unleaded in Europe, with 95% octane.

Petrol with higher octane content (SP98) is recommended for high-performance engines which put the fuel under more pressure before it is ignited, usually found in more sporty models. Some older (pre-unleaded era) cars also run better on SP98.

As to which to use, you should respect the maker’s instructions, however cars which can run on SP95 can run on SP98, but a car built for SP98 will not run as well on SP95. So, if in doubt check the booklet that came with the car.

So SP98 can allow for better performance than SP95, but only if your car is designed for it – there is no benefit to paying more for it otherwise.

Other fuels you may see at the pumps include ordinary and premium diesels (the latter may be called gazole + or diésel + and is said to keep the engine cleaner and reduce consumption), SP95-E10, E85 and GPL.

Note that SP95-E10 is not identical to ordinary SP95. It contains 90% of normal unleaded petrol and 10% of biofuel (ethanol made from sources like beetroot and sugar cane). Most cars built since 2000 can run on it, but it is less widely suited to motorbikes and scooters (they will run on it but some models can accumulate damage if it is used repeatedly).

E85 contains up to 85% biofuel and is only suited to vehicles designed for multiple kinds of fuel, called ‘flex fuel’. It is the cheapest fuel and it is now possible to buy an electronic box (costing about €400-1,000 depending on the power of the engine) which can convert an ordinary car to ‘flex fuel’ and which could make for long-term savings. E85 is also promoted as being a greener alternative.

GLP is liquefied petroleum gas, made from a mixture of butane and propane, only suited to cars designed for it.