When it the best time to perform an oil change?

You say that oil should be changed once per year or at 10,000 miles. Is it better to be changed before the winter in, say, October/November or in the Spring prior to summer, in April/ May?

Converting a car to have central locking?

The Ford Fiesta Studio model only comes with drivers side central - so you turn the key in the driver's side door and all 5 doors and the boot are open. The same for locking the car. Can anyone tell me...