JEREZ, Spain – February marks six weeks before the start of the 2015 Formula 1 championship in March.The pre-season tests in Jerez, Spain will offer early clues about whether any team can stop Mercedes from crushing the field again.The 2014 season was thrilling but that was due to the rivalry between Mercedes drivers Lewis Hamilton and Nico Rosberg, with Hamilton sealing his second F1 title in the much-hyped double-points race in Abu Dhabi.FRANTIC EFFORTSIn what was the first year of V6 turbo/hybrid “power units”, Mercedes triumphed in 16 of 19 races and finished nearly 300 points clear in the Constructors' championship.Red Bull won the other three.In the two months since Abu Dhabi, Red Bull, Ferrari and McLaren have each been frantically trying to figure out how to close the gap. Teams have been reshuffled, with four-times champion Sebastian Vettel quitting Red Bull after a miserable year to join struggling Ferrari.Double champion Fernando Alonso left Ferrari for a revamped and ambitious McLaren, a team energised by Alonso's arrival, having Honda power for the first time since 1992 and the return to the chief executive’s office of Ron Dennis.McLaren is hoping its MP4-30 car can bring back the glory days of Ayrton Senna and Alain Prost in the late 1980’s.Such aspirations are far-fetched but a first GP win since 2012 is realistic given the very experienced pairing of Alonso and Jenson Button.Alonso, who had an unhappy spell at McLaren in 2007, said: "We're prepared for a steep learning curve but it's clear that there's total commitment inside McLaren-Honda, a real change in feeling.""My motivation could not be stronger. I've done a lot of training during the break to reach my peak physical fitness."Whatever, he’s not won a GP since the Spanish GP in May 2013 and Ferrari failed to win a race through 2014 for the first time since 1993.VETTEL JOINS FERRARIVettel has little room for error and much will be expected of him. Ferrari will hope that the post-season break did Vettel some good; things became so bad the previous year at Red Bull that, according to Red Bull's team principal Christian Horner, the driver considered retiring.Williams’ drivers Felipe Massa and Valtteri Bottas will be feeling confident after strong finishes in 2014.Elsewhere, eyes will be on 17-year-old Max Verstappen as F1's youngest driver yet begins his career with Toro Rosso alongside newcomer Carlos Sainz of Spain, son of double World Rally champion Carlos Sainz.Daniil Kvyat has the task of replacing Vettel at Red Bull; given his speed and confidence that will be a challenge the 20-year-old Russian driver will relish.Eight teams will take part in testing until Wednesday (Feb 4). Caterham and Marussia have folded and Force India won't run until the second test session in Barcelona (Feb 19-22).The final session will be held a week later, also in Barcelona.