Ford Fiesta 1.4D / engine problem

I have Purchased a used Ford Fiesta which has run only 20, 000 Kms on having an assumption Ford Fiesta Diesel will give a better milleage and will be a maintanence less vehicle.From the date of purchase i regularly servicing through the authorised dealers presently the vehicle has done only 35200 and i am facing a major problem of engine oil getting mixed with the coolant and the engine has failed will it was running on the road.Vehicle was brought to the authorised dealer and they could not able to find out the problem for the last two days.If the engine is getting offed in the middle of the road, Just imagine how much risk is being involved in buying these cars???
Kindly advise how to educate the innocent buyers not to involve in such type of problems.

By V Muthuvel on Aug 25, 2009