Every car engine loses gradually power with wear. Top gear famously showed this multiple times with their older car episodes. Usually it was in 20-30% range. B

Every car engine loses gradually power with wear. Top gear famously showed this multiple times with their older car episodes. Usually it was in 20-30% range. Basically new car is a 100% system and from first kilometer / month of ageing and exposition to elements various items go down the hill. Each car type had its own set of reasons for that, but result was +-same.