Ahead of this weekend's French Grand Prix, one of the key questions many had was what specification engine would Mercedes & Lewis Hamilton be running?

Two weeks ago in Canada, the German manufacturer delayed the introduction of a second unit after a "quality issue" was discovered during testing on the dyno, believed to be linked to the crankshaft.

It was that some blamed for the poor performance in Montreal as Valtteri Bottas finished second behind Sebastian Vettel, while Hamilton floundered in fifth after also suffering from cooling issues.

The promise was it would be ready for Paul Ricard but even on Thursday, none of the drivers knew exactly what the situation was.

Well now we do and for the world champion, the news is better than he could have hoped as Mercedes confirmed not just a Spec 2 engine, but a Spec 2.1 with further improvements made in the additional time available.

“Those new components are of an upgraded specification which contains reliability and performance updates,” confirmed the team on Friday.

“This is a Phase 2.1 with some ‘added goodness’ thanks to a fantastic effort by the team in Brixworth.”

That "added goodness" likely refers to a further boost in power as even the most regimented of engineers get giddy when they find more performance.

Its impact has been pretty swift too with Hamilton and Mercedes dominating Friday practice, albeit with the tyres likely playing a more decisive role, as engines are usually turned down for greater durability.

Even so, the 33-year-old admits he did feel a difference.

“The new engine feels clean and fresh, but we won't really know its full potential until tomorrow when everyone gets to turn their engines up,” he said.

“I'm grateful for the hard work that everyone put into it back in Brixworth. They've been pushing so hard to get this engine and do it in the right way, so a big thank you to everyone back at the factory - I hope that we can do something great with it!

“Overall, it was a good session today - now we need to carry on this performance through the weekend.”

All six Mercedes-powered cars are using the new units, with Valtteri Bottas, both Williams and both Force India's all taking a second internal combustion engine, turbocharger and MGU-H in France.

The third and hopefully final engine upgrades should be expected after the summer break with two very power-hungry circuits at Spa-Francorchamps and Monza back-to-back.