Fuelling the debate: is supermarket fuel OK to use in your car?
R eader JM wrote in to ask whether his car’s engine would last longer if he used only major brands of petrol as opposed to the supermarket variety. And our consumer editor, Alex Robbins, explained how there is no empirical evidence to suggest that supermarket fuel is inferior.
This caused quite a storm, with many readers pointing out that our agony uncle, Honest John, has long recommended super unleaded. So we thought we’d better clear this up. First, Honest explains why 97-99 RON super unleaded is better for your car than 95 RON standard petrol. Then Alex explains why that doesn’t mean branded fuel is superior to supermarket fuel.
My fuel advice is based on 25 years of my own experience and the feedback I have received in around 600,000 reader letters and emails.
When unleaded petrol was first introduced it came only as 95 RON, and anyone with a car tuned for 97-99 RON leaded fuel had to have its ignition retarded.
My Golf GTIs ran badly on it. So when 98 RON super unleaded was launched I embraced it.
I then ran a series of tests (including emissions tests at a friend’s garage) and discovered that on 98 RON the engine was running a lot cleaner in terms of emissions (almost as clean as a catalysed engine) and also more economically.
Over the subsequent years I experimented with various fuels, and in comparison tests in at least 15 long-term test cars, the 97-99 RON fuel gave better mpg and better performance. Whenever a reader complained of poor performance or economy from their car I recommended a long-term switch and they all wrote back saying it had worked.
For at least the past 10 years, in order to get the best possible results in the official fuel economy tests, every car maker has optimised their engines to run on super fuels. Modern engines have sensors to automatically adjust their timing to suit different grades of fuel, but if they are optimised for the best they will always give inferior performance and poorer economy and emissions on poorer fuel.
So, that is why super fuels are better for your engine. They keep the fuel systems cleaner, they reduce emissions, they give better performance and they improve fuel economy.
My advice to JM was also based on my own experience. I’ve used supermarket fuels in both standard and high-octane “super” forms for my entire driving life without any issue in any of my cars.
Furthermore, I’ve never yet seen a conclusive result of any test that proves there is a detrimental effect from using supermarket fuel.
I’m not the only one. Edmund King, president of the AA and visiting professor of transport at Newcastle University, says: “Petrol and diesel fuel quality is governed by the same European standard, whether it is sold at a supermarket in Manchester, a motorway service area on the M25 or an independent outside Mevagissey
“Supermarkets source their fuels from all of the major producers and suppliers in the UK. All fuel sold here is tightly controlled and must conform to specifications.”
David Bizley, the RAC’s chief engineer, adds: “There is no difference between standard 95 RON petrols as long as they are purchased from a reputable supplier, so motorists should not have any concerns about petrol quality.
“But they should always be concerned about price, which can vary dramatically.”
Of course, there is also the separate question of whether 97-99 RON super unleaded, available at supermarket and branded fuel stations alike, is better than the 95 RON stuff.
Here the advice remains that super unleaded results in better performance, economy and engine life. That said, with super costing 9p per litre more on average, one must always work out for oneself whether the gains are worth the extra cost of the fuel itself.
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