Ford fiesta, 2015, 49,000 miles Engine light came on in March, no obvious change in car behaviour, was due a service in April so fully serviced and ran fine till last month Engine light back on, into garage, was told there's nothing obvious and the engine fault code suggested maybe the car maybe sat around a lot. Car is used 40 per day miles mon - fri. Was suggested I put some engine cleaner in the fuel and that would assist the problem. Got that done, charged me 30 quid for it, now i trust this guy with cars he has serviced me and families cars for years. Engine light came back on 3 weeks later. How worried should i be? Its got a lot of miles for its age, car has felt no different all 3 times light has came on, feel a little confused that the mechanic seemed unsure of the exact problem.