Before the Spanish Grand Prix everybody, but perhaps the most avid supporters of Lewis Hamilton, was hoping that the fight between AMG Mercedes and Ferrari would intensify as the teams have brought their first big aero updates of the season. But alas, it all ended up being rather a damp squib.

Instead of getting closer, Ferrari’s gap in qualifying was back to Malaysia proportions. In the race, the gap between Mercedes and the next best team in 2015 was the largest of the season to date.

On an identical race strategy to Rosberg, Sebastian Vettel lost an average of 0.687 seconds per lap to Rosberg and the Mercedes driver didn’t even push particularly hard for most parts of the race.

So why has the gap risen from 3.9 seconds in Bahrain to 45.3 seconds in Barcelona? Particularly when Ferrari’s race pace has been within tenths of a second per lap of the Mercedes duo.

Auto Motor & Sport‘s engineering expert, Michael Schmidt, insists that a gap so large cannot be explained by track characteristics and updates alone. Not even the fact that all Mercedes powered cars now have the ‘power mode’ of the unit for 100 kilometres longer than Mercedes initially specified – is enough to explain this sudden difference because Rosberg did not use that additional boost for most of the race.

One explanation is that the Ferrari unit has lost some power. In Bahrain, the FIA mandated the fitting of additional fuel flow sensors to preempt the engineers creating a fuel reservoir beyond the original sensor.

There has been a theory abroad suggesting that certain engine fuel delivery systems have been pumping fuel through the original sensor at the maximum rate – regardless whether the engine is using it or not. The unused fuel is stored and then when required injected into the ICE at a higher fuel flow rate than the regulated limit.

According to Schmidt and other experts, such a system is worth three to four tenths of a second per lap. It is particularly effective following corners that require maximum traction – like Barcelona’s third sector – where Ferrari lost consistently over half a second per lap.

During Q1, one car was caught with suspicious sustained fuel pressure peaks in the range between 90 and 100 kg/h. As later transpired – it was an AMG Mercedes car. While the team was apparently able to provide a plausible explanation, Schmidt believes that the German team did that deliberately to raise FIA’s awareness in the matter.

The FIA were remarkably swift to respond. At 15:05 local time on Saturday a technical directive was issued that stated sustained fuel pressure peaks in the range between 90 and 100 kg/h would not be tolerated.

The fuel flow peaks were absent from all the FIA’s measurements during the race, but Ferrari were now noticeably more anaemic.

Tinfoil hats time.