The specific oil for a Ford Fiesta depends on the year and engine of the car. Ford recommends checking your owner's manual for the exact specifications, including the weight (e.g., 5W-30, 0W-20) and type (synthetic, synthetic blend, conventional) of oil. The manual will also specify the correct oil filter.
Don't rely on general advice found online; always consult your owner's manual for the most accurate and up-to-date information.