The team's new car, the MP4-16, has dominated the timesheets at the Valencia test track in Spain.
Mika Hakkinen and David Coulthard were quickest at the end of every day.
The Scot was at least three-quarters of a second faster throughout the test than any other team's new car.
Even without the presence of McLaren's arch-rivals Ferrari in Valencia, that is a worrying sign for McLaren's opposition with the season starting in Australia on 4 March.
Pre-season testing times are notriously unreliable indicators of form, but the McLaren's pace has been impressive even with that rider.
Ferrari's form is a complete unknown -they have been testing alone in Italy.
Coulthard was over 0.75sec ahead of the Jordan drivers Heinz-Harald Frentzen and Jarno Trulli on consecutive days while running in the dry.
In the wet on Wednesday, the final day of the test, he was two seconds fastest than the next car.
Test driver Alexander Wurz made it a one-two for McLaren, driving the team's 2000 car, which is adapted to comply with new rules imposed for this year.
Optimistic
Meanwhile, at Fiorano in Italy, Ferrari's Luca Badoer completed a three-day test for the team.
At the Estoril circuit in Portugal Jean Alesi put the Prost team top of the times in the new AP04 on the eighth day of testing.
The Frenchman followed up Prost test driver Pedro de la Rosa's fastest time on Tuesday.
Benetton's Jenson Button was more than a second adrift of the Frenchman but the team's technical director, Mike Gascoyne, said he was pleased by the test.
"It's been satisfying today as we got a good long run in again on the new car and got a further engine up to mileage," said Gascoyne.
"Each time we have done this we have made good progress with the chassis and our times reflect this."