The McLaren drivers Fernando Alonso and Jenson Button will start last in Sunday's Belgian Grand Prix after being hit with heavy grid penalties for changes to their Honda power units.
The Mercedes driver Niko Rosberg recorded the fastest times in practice at Spa despite an explosive, high-speed tyre blowout that had the German wrestling to keep the car out of the barriers.
The order at the top was the same in both sessions, with Rosberg ahead of team mate and championship leader Lewis Hamilton with Red Bull's Australian Daniel Ricciardo third fastest.
The Spaniard Alonso was given a drop of 30 grid positions, despite only 20 cars being entered for the race, while his British team mate Button collected a marginally less draconian 25-place penalty.
They could add to the meaningless, if eye-catching, tally if as expected their team takes advantage of a rule change by swapping out the power units again on Saturday.
Previously, any untaken grid drops were translated into time penalties during the race but the rules have been amended to ensure that the maximum sanction is to be sent to the back of the field.
That means McLaren could give themselves two penalty-free units for future races if they switch the undamaged ones again over the weekend for new ones after already incurring the maximum drop.
The race stewards issued statements containing a long list of components that had been changed in breach of the regulations.
In Alonso's case, the double world champion picked up a 10-place penalty for using his seventh internal combustion engine of the season.
There were four five-place penalties for replacing other elements of the power unit.
Honda have been allowed a maximum of five power units per driver this season, one more than other teams because they are new manufacturers.
"We've used seven or eight engines...and we are in the 11th race so definitely our position is not great in terms of reliability," said Alonso.
"If we had more of a penalty than starting last, we would accept it because this weekend is just a test for us."
Button collected a 10-place hit for using an eighth turbocharger and three five-place penalties for exceeding his allocation of other parts.
The penalties were expected by both McLaren drivers, who have endured a nightmare start to their team's new partnership with Honda, even if Alonso's punishment was greater than anything they had so far experienced.
In Austria in June, before the rules were changed, both drivers were given 25-place drops for engine and gearbox failures.
Honda had promised McLaren an improved engine for Belgium but the team recognised the upgrades would incur penalties. The stewards said the FIA had been notified of the changes on Tuesday.
"I am confident that our reliability problems are now behind us, which means we can turn our attention to increasing power," said Honda motorsport head Yasuhisa Arai earlier this month.
McLaren, the second most successful constructor in the sport's history after Ferrari, are currently ninth of 10 teams.