Budapest: McLaren's Lewis Hamilton was fastest in both practice runs for the Hungarian Grand Prix on Friday while Red Bull, hit by a new rule banning a controversial engine setting this week, endured two slow sessions.
In another rain-hit practice session, the British driver clocked a best time of one minute 21.995 seconds, slightly better than his first time, followed by Kimi Raikkonen of Lotus and Williams's Bruno Senna.
Seven-times champion Michael Schumacher slid off the track and crashed into a wall of tyres as the second session was hit by a brief but heavy summer shower, having started in warm sunshine.
Red Bull's drivers, who failed to make the top 10 in the first session, were well down the pecking order again.
Sebastian Vettel was eighth and Australian Mark Webber, second behind leader Fernando Alonso in the Formula One championship, 14th.
Both were unhappy but said this week's ruling was not to blame.
McLaren have looked much stronger following performance upgrades made to the cars after a disappointing performance at Silverstone and Hamilton was delighted with the car's performance.
"It's been a really positive day. I'm very, very happy," said Hamilton. "We made some good changes to the car…and we're on the right path, but we've still got some work to do.
"The Red Bull looks very quick, so does the Lotus, and obviously the Ferrari as well, so we're by no means feeling comfortable."
Ferrari were also impressed with their rivals.
"McLaren remained unbeatable today and will be the clear favourite for the remaining part of the weekend," they said on Twitter.
McLaren's team principal Martin Whitmarsh was more cautious.
"You're not pleased until you're scoring maximum points," he told reporters. "We've made some progress but this has been a very difficult to predict championship."
For the third race in a row, rain affected the practice day limiting the amount of testing the teams could do.
"We did not manage to try the dry tyres over a long run but, at least in the morning, we managed to complete the work relating to the aerodynamic updates which we brought here in Hungary," said Alonso, third in the morning and fifth in the afternoon.
Red Bull have a reputation for keeping a low profile in practice but their drivers admitted they were not fully satisfied.
"We've got work to do," said Webber, who was an uninspiring eighth in Hockenheim on Sunday as he lost ground on Alonso.
"We seem to be going OK in some places, but losing time in others - so we'll go through it tonight. I need to work on the balance. There's no change from the engine mapping amend."
"There is a lot of room for improvement," said Vettel, adding the effect of the engine ruling was "much less than people expect."
Red Bull were forced to change their engine torque mapping after the governing International Automobile Federation (FIA) closed down a loophole in the regulations this week.
The new ruling, addressing a hugely complex issue, limits how much teams can change specific settings that control the amount of torque delivered by the engine in various conditions.
Red Bull were referred to the stewards over the engine torque mapping before last week's German Grand Prix. They were cleared of breaching the regulations but the FIA made it clear in its wording of the decision that it was not happy with the situation.