The Fiesta manual lists oil/filter changes as every 10,000 miles. The ST supplement does not have its own interval chart, so I would assume that - like everywhere else does - the dealership is trying to get you to go more often than is required.
The car comes with, and is recommended to use, semi-synthetic blends. I will however be using full synthetic (Amsoil or similar) since it's a turbo and does make a difference.
The car comes with, and is recommended to use, semi-synthetic blends. I will however be using full synthetic (Amsoil or similar) since it's a turbo and does make a difference.