There is no evidence to suggest that supermarket fuel is inferior quality, as they conform to the same British standards as any other fuel sold and are supplied by many of the same large refineries. Premium fuels such as Shell V-Power may offer additional benefits thanks to additives designed to reduce wear, but you should experience no problems from using supermarket fuels.

Fuel additives may bring additional benefits in terms of engine cleanliness, but it is a matter of balancing the expense of additional products against what you are trying to achieve. Timely and comprehensive maintenance is the most important factor if you aiming for reliability and longevity of your vehicle.