|>>|| No. 4530
Tesco's 99 is good and is what I run my silly cars on. Factory tuned sports cars often seem to be tuned to run best on Shell V-Power, but you have to be on the nerdiest side of car nerd before you're thinking about those sorts of marginal gains, and if you're that much of a mentalist you'd just tune it for Tesco 99 if you wanted to save a few pennies.
In general, for an average car you'll save about three quid per tank. A bottle of fuel system cleaner/fuel additive is about three quid too, and using one of those every single time you fill the tank is overkill, so unless shell's additives are fucking fantastic, then Asda fuel plus some sort of shop bought additive like redex every three fills would almost certainly be the same, if not better, than branded fuel.
As said, with my old diesel v8, I can tell straight away that it likes to run on shell - you can hear the difference, and feel it, and I don't think it's placebo at all, as two of my car nerd friends have commented unprompted before that my car sounded lumpier, and this was when I had to put Tesco in it.
But, of course, other than lexuslad, I'm willing to bet nobody else here is running a finicky car from a decade or two ago, so I would absolutely not recommend using branded fuel for your car. I would also say that the difference in price is not really huge, so I wouldn't worry about it. The most cost effective petrol is likely the one that is closest to you, is at the supermarket you already shop at, or directly on your route to work etc.
Also, Shell used to actually balance out, when they did loyalty points - you would actually end up with cheaper fuel than anywhere else if you used them exclusively. They've changed the system now to one where you get about two quid off every ten visits, which is just exponentially worse a deal.