Good day

I was driving my wifes Hyundai Getz 1.6 (App 138000km on the clock) and heard a ticking noise, the oil light was coming on and flashing like my indicator. I stopped and checked the oil level, it was full. I drove for another 15km when all of a sudden I heard a knocking noise and lost all compression. The car could still have been driven. I have been looking at the piston slap forums and people are saying it only happens when the car is cold. My wifes car was hot when the noise started and when I started it the next day still made the noise. Could it be dirty hydraulic lifters as the oil was filthy when I drained it. I have taken the head off and before I strip the motor and send it for engineering was hoiping somebody could answer my question. I did not blow a gasket, the car just lost compression. I was in 5th gear and my foot was flatr and the spedometer did not clime. I hope all the info assists you in trying to help me.

What is the allowed gap for pistons to play? 0.025mm?