More is less: Save money by buying more expensive fuel
‘Spiralling fuel costs mean most motorists are looking to spend as little as possible to fill up, which makes super unleaded fuels seem an unnecessary expense for all except the highest performance cars. But spending more per litre could pay dividends in the long run.
‘Super unleaded fuels have a higher octane rating, so are more resistant to igniting prematurely, which means a greater share of fuel is burnt only when the engine wants it to. High performance engines with turbo or superchargers usually create enough heat for low octane fuel to ignite early in the cylinders, which can reduce power and create sooty deposits inside the engine over time.
‘But manufacturers are chasing ever-higher performance from small engines, so most mainstream petrol cars now feature some sort of turbocharging. It means while the family hatchback only produces 115bhp, there could be a 1.0-litre petrol engine working hard to produce it. These present ideal conditions for fuel to ignite prematurely under load.
‘Traditionally the problem was worsened by injecting petrol before the cylinder. Modern petrol engines inject it directly into the combustion chamber as its needed, which can reduce the possibility of pinking or pre-ignition. But consider these as high performance for their size, and using super unleaded starts to make sense.
‘I’ve tested this on my long-term SEAT Ibiza 1.2 TSI. For the first 1,800 miles it ran on normal unleaded fuel, and averaged just under 40mpg on the motorway. Using V-Power with no change in driving style, it climbed to 43mpg. I’ve since tried switching back and the economy dropped again, suggesting regardless of what’s recommended the hard-working engine prefers higher octane fuel.
‘Based on prices at my local Shell station, a 20,000 mile year using V-Power would cost £3,042.73, while the same distance using 95RON unleaded would cost £3,111.79. While high octane fuels won’t benefit all cars, it could pay for any extra cost when used in a new-generation downsized unit.’