depends what year,after 04 the waste gate is electronically actuated so they go wrong,if you dont fit original fuel filters these can flash a warning light and put the car in limp home mode.i have an o4 ghia estate,every month im buying something so its getting sold,64k,this month has had a wheel bearing,silencer box,heater control panel as that broke and the heaters didnt work,sidelight fuse.
it now needs a new set of speedo clocks as they stopped working after the car went into the oven after having a door painted and i replaced a spring about 2 months ago as 1 broke.
i wouldnt buy an older mondeo again,made of shit.great car when its working but i think id buy a petrol,maybe you get less mpg but how much fuel could you buy for the price of a set of injectors,a pump,a dpf,a turbo etc?more than what you would have saved in the amount of miles you get before it breaks