Using premium fuel in a car designed for regular unleaded petrol can lead to the build-up of carbon deposits on the engine valves and injectors. This can eventually cause problems such as engine knocking and misfiring.
In addition, using supreme fuel in a car that is not tuned for it can actually decrease performance. This is because the higher octane rating of supreme fuel does not provide any benefit to an engine that is not designed for it.
If you want the best possible performance and fuel efficiency for your Citroen Xsara, it is best to stick with regular unleaded petrol.
