Mazda Repair: ticking noise from engine, piston slap, mazda 6

Question
Hello,
I have an 03 mazda 6 2.0 diesel ts2.
The engine has a knocking/ticking sound when you raise the revs and a smell of burning oil. Also the oil light flickers sometimes when I come to junctions. I spoke to a mechanic and his answer was replace the engine! I've only just purchased the car so i'm hoping thats not the only solution. Any help would be greatly appreciated.
Thank you.
Mark.

Answer
a knock and a tick is very different when it comes to cars if you here if from the top engine you may just have to have the valves adjusted if it's a lower end noise then it's probly a piston slap or the connecting rod a good mechanic will be able to trace the sound of the noise and advise you better you don't have to replace the motor may just have to replace major engine parts sometimes depending on the repair it's cheaper just to replace the whole motor