I don't take the Telegraph but I do follow Honest John on-line. I was talking with a pal about a Tesco 10p a litre discount offer and he says that that's the only time he uses supermarket fuel - the rest of the time he uses Shell Fuelsave which I think is their 95 brand.
Hesitate to bring this old chestnut up again but I looked through a number of Q and A responses on Honest John's website and he definitely has a thing about supermarket fuel. He says that it is all in the additive package and the supermarkets put the bare minimum in as mandated by law. He, personally, puts Shell V Power in a Fiat 500 and BP Ultimate diesel in a Mazda that he own. He denies any connection whatsoever to the oil companies concerned, indeed his focus is on supermarket fuel v branded. He says this is based on years of correspondence with motorists and 50 years driving experience.
He also says that he "knows for a fact" that all car manufacturers have their cars optimized to run on 97 RON or above fuel and that, when EDC and now WLTP tests are done, all cars are tested using branded super fuels. In short your car will run better and more economically on Shell V power or any other branded equivalent.
Is he right? I guess supermarket fuel will do the job and any damage will be many many miles down the line but he is adamant on this.