engine stopage in flight

What engine? Age and total hours

Do you mean AeroShell Oil Sport PLUS 4? Frequency of oil and filter change

hi 

   for the frequency for change  the mecanic told me every 50 hours 

Knowing nothing else, I would guess you have been overstressing the engine.

Fixed or Variable Pitch Prop?

What RPM do you see in the takeoff climb at WOT?

And what RPM and Manifold pressure do you routinely cruise at?

hi

    the  engine is monted in a DA 20 KATANA  with variable pitch propler sorry for my bad english .

Hi

We had the same problem 10 years ago, but at that time

The conrod was broken from the small end.

Check the lubrication system.

the picture shows lack of oil case the conrod to broken.