Naturally-aspirated engines generally have much lower official fuel economy figures, but they usually perform close to these in the real world. They don't have as much power low down in the rev range as turbocharged engines, meaning they can get bogged down unless you're willing to change gear regularly and hold onto revs - this is especially true when tackling hills or overtaking. They tend to be very reliable. Turbocharged engines have more power available low down, meaning they feel quicker and are easier to drive without having to change gears regularly or hold onto revs. They often have very impressive official fuel economy figures, but our Real MPG data (www.honestjohn.co.uk/real-mpg/) reveals that many owners don't see close to these in the real world. Some turbocharged engines have had reliability issues, too.