Mercedes upgrades for F1 Spanish Grand Prix enter Formula 1 loophole territory

Mercedes arrived at the Spanish Grand Prix after making improvements to their W08 vehicle and after Friday's practice sessions Lewis Hamilton and Valtteri Bottas were both impressed with the new offering.

Hamilton's best effort of one minute and 20.802 seconds saw him finish 0.090 secs ahead of Bottas - a victor last time out in Russian Federation - with Kimi Raikkonen leading Ferrari's effort in third and Vettel trailing only in fourth.

After dominating the opening three races of 2017, Mercedes were initially forced onto the back foot in Sochi as Sebastian Vettel took pole ahead of Ferrari team-mate Kimi Raikkonen.

Last year's Spanish GP victor Max Verstappen was again ahead of teammate Daniel Ricciardo, a tenth up on the Aussie and 0.636s off Hamilton's lap.

Hamilton has one win this season and two runner-up finishes to Vettel, who leads the British driver by 13 points.

"I don't think there is a particular pattern yet", he said.

"We expected Valtteri to develop through every single race and step up his performance and he's shown that", Wolff said.

"They have done an unbelievable job, the team, with these upgrades and the auto is working just as we hoped and expected", said a happy Hamilton after his sizzling show on a cool and cloudy day in the industrial hinterland of Barcelona.

"I didn't get everything together, I wasn't too happy but I can feel the auto is quick so that is good".

"I've said from the beginning of the season that he was in competition, so it's no surprise that he would eventually get a win", said Hamilton.

"And now it's done, I just want to do it again and again". "If from here to September-October we are in a position where we see clearly a possibility to win in 2018, I will be more than happy to stay with the team. So, we are taking this season one race at a time".

"Lewis had a hard weekend in both qualifying and the race", said Wolff.

"It's not my decision but I'm ready to race whoever comes along".

As Raikkonen improved to 1m 22.456s, so Vettel fell to fourth, lending Mercedes an unexpectedly big early advantage.

"We are a little closer to Ferrari and Mercedes brought a very good update so I think they are still ahead, but it was a positive day". "I'm happy with what we brought; some of the stuff you can see, some of the stuff you will not see, so no secrets but the usual work".

"And I think it's a very good challenge to try and beat them".

With warm and windy conditions making it tricky for teams and drivers to find their form around the Barcelona venue, particularly on the softer rubber, Vettel would end his day four tenths down on pace setter Lewis Hamilton.