Lewis Hamilton insists he is still happy with the pace of his McLaren despite coming off twice during the third day of testing in Jerez.
Hamilton climbs out of his car after beaching it at the Jerez circuit
The 23-year-old blamed the lack of engine braking and traction control, now banned under new regulations, as he twice beached the car in gravel.
"Without these controls helping you on the entry to corners there is more locking of the rear wheels," he said.
But Hamilton added: "I think we've got off to a really good start."
Hamilton, who missed out on the world title by just one point in his rookie season last year, was one of several drivers to skid off in wet conditions in Spain.
But despite his problems, Hamilton set the second fastest time of one minute, 20.099 seconds.
"The first time it was just wet," he added. "I touched the kerb and just went on to the edge of the gravel - it would be good if there were some proper run-off areas here - and then it was the same again in the afternoon.
"Without these controls helping you on the entry to corners there is a lot more locking of the rear wheels, and when you are on the limit and pushing that is what happens.
We're moving in the right direction and we just need to keep on chipping away
"I'm getting used to being without traction control and developing the car. But it is so slippery, and even harder without traction control.
"Without these controls it does make it a little bit nervous on exiting corners, which makes it a lot easier to make mistakes. But you just have to try and deal with it the best you can.
"All the teams will have to work hard to understand how to use the power better."
Following a private test last week, Hamilton is convinced of the new car's reliability, adding: "Even compared to last year it was a big improvement when we went to the first few tests to see the reliability of the car.
"We're moving in the right direction and we just need to keep on chipping away."
Toyota rookie Timo Glock, who replaced fellow German Ralf Schumacher at the end of last season, ended the day at the top of the times finishing 0.3 seconds ahead of Hamilton with a time of 1:19.779.
Hamilton's former McLaren team-mate Fernando Alonso was third for Renault while champion Kimi Raikkonen ended eighth fastest in his Ferrari.
David Coulthard had a frustrating day after his new Red Bull RB4 broke down on its debut.