SAKHIR, Bahrain - Formula 1 teams wrapped up pre-season testing in Bahrain on Sunday (Mar 2 2014) with Lewis Hamilton on top of the time sheets and his Mercedes team the clear favourite for the season opener in Australia on March 16.The 2008 champion completed 70 laps of the Sakhir circuit and ended the final day with a time just 0.02sec off the best lap of the week set by Brazilian Felipe Massa for Williams on Saturday, which itself was just under the qualifying time for the 2013 race there.Hamilton, whose team did more laps than any other over the 12 days of testing in Spain and Bahrain, said: "This has definitely been the most challenging winter I've experienced and the car is still very much a work in progress but we've learned a lot over the course of these last few weeks."Overall, it's been a good winter of testing for us."'SO MUCH TO LEARN'F1 has undergone the biggest technical revolution in more than 20 years with the introduction of a turbocharged V6 engine mated to energy recovery systems.Hamilton added: "There's so much to learn with these new cars - I don't think anybody can be fully ready for the challenge of this season but I feel as ready as I can be and I'm looking forward to seeing where we are in Melbourne."Williams was second-fastest on Sunday but recorded more distance than any other team on the day - Valtteri Bottas racked up 108 laps. Ferrari's Fernando Alonso was third (74 laps) in a session that was extended by 30 minutes to allow teams to test under the floodlights which will be used for the Bahrain GP in April.While Hamilton can head for Australia with confidence high the 2013 champions team, Red Bull, plenty of catching up to do. Four-times champion Sebastian Vettel recorded his best distance in a day - 77 laps - but was 4.10sec slower than Hamilton's best time of 1min33.278.Vettel has yet yet to complete a race distance in testing as Red Bull struggles to get its car working reliably with the new Renault power unit. He complained: "We cannot do the times that the guys at the top are doing, and for a couple of reasons, but we have bigger problems to solve than just the pace."Surely things will calm down. We have to use the two weeks that we have until then to fit new parts to the car and build it to the best knowledge that we have."'NOT AN IDEAL SITUATION'Lotus, which missed the first test at Jerez in southern Spain, also recognised its cars had plenty of catching up to do. Romain Grosjean managed only 32 laps and was slowest on Sunday's time sheets after being sidelined by more power unit problems."We're not in an ideal situation," he admitted. "There is a lot of new technology for everybody to understand but even though we have stopped many times and spent a lot of time in the garage, each time we run the car we are learning something new."We now have two weeks to find a lot more performance and reliability."Mercedes-powered McLaren also hit problems: Jenson Button was halted by a high-mileage engine failure and then an electronics problem.The delays meant the team was unable to get driver feedback on a new front wing that arrived on Sunday morning.