(CNN) Lewis Hamilton may have kept his powder dry in practice for the Belgian Grand Prix Friday, but the Mercedes driver will need all the pace he can muster to keep his title challenge on track this weekend.
Hamilton, who leads the F1 championship by 19 points following the summer break, was 13th fastest on a warm day at the Spa-Francorchamps circuit.
He will be forced to start from the back of the grid come Sunday, having exceeded the prescribed number of engine part changes cars are allowed in a season.
Hamilton was given a 30-place grid penalty on a day when local favorite Max Verstappen was fastest in qualifying.
The Briton has already overcome early season problems with form and his car to wipe out a 43-point deficit to Mercedes teammate Nico Rosberg in the overall standings and revive his hopes of winning a fourth world title, and third in a row.
"In terms of winning, it's going to be very, very hard," Hamilton told reporters.
"But I'll do everything I can."
Mercedes had "not ruled out the possibility of (Hamilton) using even more fresh parts prior to Saturday's qualifying," the official F1 website said.
This would earn a further grid penalty, but Hamilton is already at the back of the 22-car field and the sanction cannot be carried over to the next race.
His car can thus be loaded with up with fresh equipment for the eight races left after Spa.
Fernando Alonso is also set to start Sunday's race at the back of the grid for McLaren after he replaced his power unit with a fresh one following Friday's session in unexpected heatwave conditions.
Later, the Spaniard reiterated his frustrations over the current state of F1, saying he will wait to test a 2017 car before deciding on his future.
"In the last couple of years, in this turbo era, the cars are different to drive," the two-time world champion said.
"But I was lucky to drive the 2004-2005 car, and even in 2009, they were more extreme F1 cars. When I see a GP2 car is three seconds slower than FP1, I feel a bit sad.
Read: Hamilton wins German GP to extend lead
"Next year, if the cars are fun to drive and exciting to drive, I will probably stay longer in F1. But if the cars still give me the feeling of the last few years, I will stop."
On the track, Rosberg was fastest in the first session of the day but Red Bull's Verstappen led the way in the afternoon session.
Born in Hasselt just 50 kilometers away from the Spa-Francorchamps circuit, the 18-year-old Dutchman drove the fastest qualifying lap with a time of one minute 48.085 seconds.
"I'm happy to be first in front of so many Dutch fans but it's still not qualifying and not the race so let's see," he said.
"When I went up to first position in the second practice the fans were all cheering me on with their flags. It definitely gives me a boost and motivates me a lot."
That allowed him to outpace Australian teammate Daniel Ricciardo by two-tenths as the Austrian outfit continued its resurgent form.
Meanwhile, Rosberg was one of several drivers to trial the new halo head protection device Friday.
"The team have done a great job on the halo. It doesn't disturb me when driving," the German told reporters.
"I could go fast straight away and even set the best time of the session with it this morning, so I think that was a success."
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Red Bull has been trialling an alternative "aeroscreen" design to the FIA-sanctioned model, which is due to be introduced in the 2018 season.
"From a visibility point of view, it wasn't too bad," team boss Christian Horner told reporters at Spa after Ricciardo also tried the official three-pronged cockpit protection system. "There were some restrictions around the side, but it is a work in progress."