As we all know, Mercedes was forced to install on old Power Unit in Nico Rosberg’s car prior to Qualifying in Italy. The cause of failure with the new engine Nico was running was ascribed to a “water leak.”

Of course with a handful of laps to go, Rosberg’s older engine failed, providing some graphic images of a smoking W06 being hoisted away by a crane.

Mercedes have now revealed more detail of the issues Rosberg suffered with both the new and old power units.

“We let Nico down on two occasions with a pair of mechanical failures,” says Paddy Lowe. “Which unfortunately nullified a great recovery drive that should have brought at least a third-place finish,”

According  to Andy Cowell, in the new #PU3, water was found in the oil which has been attributed to a ruptured heat exchanger, but he also alluded to a potential problem with the cylinder head gasket.

Cowell said the failure of  PU#2 was due to piston damage.

“Burning a piston” as they call it sounds reasonable. We know Nico had been told to turn up the output of the engine in the final stages of the Monza race, just before it blew up. The previous wear on that power unit engine due to the mileage it had covered was probably a significant contributing factor.

Mercedes now say this unit had covered 3615 Km on it at time of failure. (The Judge13 ‘Chancery’s’ estimations were 3522 km for #2, less than 100 km difference).

In Singapore, Rosberg will be using the refurbished #PU3 which had been removed before qualifying.

However, the decision to put a power unit in that was been tainted with water in the lubrication system is somewhat bizarre. It is difficult to explain why any motorsport team would race with an engine that had confined contamination let alone a questionable head gasket.

With seven races left, one wonders why Mercedes haven’t written off #PU3, or use it only for practice sessions and install PU#4 for Rosberg immediately.

This would likely see Nico having to take a penalty for ICE #5 at some point. Yet, unlike the other F1 engine manufacturers who have replaced multiple parts of the PU and amassed big grid penalties, Mercedes would only need to replace the ICE, for a maximum grid drop of 10 places.

Even with the penalties, Nico would almost definitely score good points and even make a podium if he started P10, 11 or 12.

However, should Rosberg have another failure with #PU3 in the heat of Singapore he is likely to lose his second place in the championship to Sebastian Vettel – and still suffer having to use #PU5 at some point before the end of the season.