Lewis Hamilton was in command leading team-mate Nico Rosberg by six tenths of a second in afternoon practice at Spa.
As the soft option tyres came out of their blankets for the first time this weekend, Hamilton lowered the benchmark to a 1:49.189 as his Mercedes rival made a slight error on his quickest run and Fernando Alonso retained third for Ferrari as the Mercedes-powered threat again failed to materialise.
Red Bull hit trouble
As Ferrari go against the perceived Mercedes domination, Red Bull continue to struggle to join the party.
Sebastian Vettel's engine problem for the morning forced him to miss the entire afternoon with only the monocoque of his RB10 sat on the stand in the garage. That put the pressure on Daniel Ricciardo to produce the data and complete the running on both compounds of tyre, however, he too had some issues.
With the low downforce configuration, the Australian's skinnier rear wing was causing problems as the DRS flap caused a lot of instability when closing under braking for Les Combes.
With more valuable time lost, Ricciardo then struggled on his single lap run on the softer compound rubber though the fact he was still eighth despite his scruffy lap is some cause for optimism.
Williams upping the ante
After a somewhat usual low key morning session, Williams began to show some of the form we are expecting as Felipe Massa and Valtteri Bottas moved towards the sharp end of the standings.
The two drivers were fourth and sixth respectively and again still seemed to be hiding their absolute true pace.
Just behind Toro Rosso showed better pace as Daniil Kvyat ended the day seventh and the fastest of the Red Bull cars.
Force India dropped back slightly from their promising morning positions, indeed Nico Hulkenberg was the only driver in the top 10 as Sergio Perez was only 13th, but McLaren were able to maintain both cars in the important Q3 positions as Jenson Button was fifth and Kevin Magnussen ninth.
King of Spa struggling
It was another bad day at the office for four-time Spa winner Kimi Raikkonen. The Finn had ERS problems in the morning and in the afternoon had very poor grip in his Ferrari.
During his single tyre lap on the soft compound, Raikkonen could only achieve 15th place and during his race simulation was just as uneasy at the wheel describing the car over the radio as "poor".
It seems, however, any hopes of Williams being a match for Mercedes could be rather farfetched. The two Silver Arrows have at least a second based on second practice times over one lap and then over the race simulation that gap continues to exist.
With the higher fuel both Hamilton and Rosberg were running consistently in the 1:54's while a few could only manage a handful of laps in that same bracket before dropping into the 1:55's.
The more aggressive tyre choice by Pirelli this weekend, with the soft and medium, appears to have opened up a few different strategy options for the race.
The yellow-marked softs are over a second per lap quicker than the harder white-striped mediums and are lasting for around 15 laps.
In the battle of the Mercedes, Hamilton appears to have the slenderest of advantage's over Nico Rosberg, on race pace the pair were identical although the German was slightly easier on his tyres than the Briton.
But when its all about position it appears Lewis is the one to beat come qualifying on Saturday, however, we have said that several times recently only for trouble to strike at just the wrong time. Add to that too an increased threat of rain and around Spa quite literally anything could happen.
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