( 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 ##l warns that Mercedes have not peaked yet . Mercedes have won all four Grands Prix so far this season . Rosberg leads drivers ' championship race . Spanish Grand Prix takes place in Barcelona this weekend .