( CNN ) -- It 's a warning which will reverberate around the Formula One paddock with more gusto than the sport 's much derided V6 engine . Nico Rosberg , says the sport 's dominant team `` definitely has n't peaked yet despite Mercedes having won all four of the season 's opening races . `` At the beginning of the season we had the car we developed in the winter and now we 're going to keep on pushing , '' championship leader Rosberg told CNN 's The Circuit . `` It has been three weeks since the last race and the development rate is so fast . We have 600 people back in the factory working crazy hours to make this car faster in every single race . `` For example , from the start of the season to the end of the season , you can have a car that is 1.5 seconds quicker by the end just with new parts on the car . `` It 's a good period for the team at the moment . We really have the momentum , a quick car , the best car in F1 -- the Silver Arrow . '' The Mercedes car 's next outing is at Sunday 's Spanish Grand Prix , providing Rosberg and teammate Lewis Hamilton , who already has three race victories to his name this season , the opportunity to make another giant statement of intent . Hamilton and Rosberg have finished first and second respectively in each of the past three races , but the German is hoping he wo n't have to play second fiddle to the 2008 world champion for a fourth consecutive race . `` At the moment , it has been all about the battle against my teammate but of course , we 're all conscious that the other teams are flat out pushing trying to close the gap and we need to keep doing a good job to stay ahead , '' added Rosberg . `` I 'm just looking forward to the next race and getting the most out of it . It 's a tough battle with my teammate at the moment and I need to try and come out on top in Barcelona . '' While Mercedes has enjoyed a stellar start to the 2014 season , there is no sense of complacency , with Ferrari , Red Bull and Lotus all striving to produce improved performances in Catalonia to prevent the drivers ' title becoming a two-man race . `` The first European round of the year always provides a prime opportunity for teams to arrive with improvements to their cars , '' Mercedes executive director Toto Wolff told the F1 website . `` Of course , we are no different to any other team in that respect and our aim must be to increase the advantage we enjoyed at the last race in China . `` We have seen already that our rivals are relentless in their efforts to close the gap . As a team , it is up to us to rise to that challenge -- to take that relentless mentality to an even greater extent than those around us . `` If we are to build a sustained level of success in this sport , any small advantage must be seen as a platform upon which to build a bigger advantage . `` We head to Barcelona on good form and in high spirits . But , most importantly , we approach the next race weekend as we approached the first -- in the knowledge that there is still a long season ahead and anything can happen . ''
Nico Rosberg warns rivals Mercedes have not peaked yet . The German driver has been on a roll of late, winning the last three races and leading every lap in qualifying for his first race since suffering an engine failure at the start of this season. Rosberg leads drivers ' title race . Spanish Grand Prix takes place in Barcelona this weekend .