Kubica won the race in his fifth attempt, his first three in the second tier LMP2 category, to become Poland's first overall winner since Le Mans was first staged in 1923.
McLaren's Lando Norris won the Sao Paulo Grand Prix to surge 24 points clear in the Formula One championship on Sunday.
Oscar Piastri led McLaren teammate and Formula One title rival Lando Norris at the top of the timesheets in sole practice for the Qatar Grand Prix on Friday.
Lando Norris can be crowned champion on Sunday but a win for Oscar Piastri would take the battle down to a final showdown in Abu Dhabi next weekend.
Toyota Gazoo Racing, the Japanese car maker's motorsport division, will become title sponsor of the Haas Formula One team next season in a deal that strengthens an existing technical partnership.
The 40-year-old, who won six of his world championships at Mercedes, also unveiled a new bright yellow helmet, as he continues his first official week at Ferrari which began at the team's headquarters on Monday.
Hamilton, 40, is getting in some laps behind closed doors with teammate Charles Leclerc under rules that allow a limited amount of track mileage in older F1 cars.
The seven-time world champion, the sport's most successful driver with 105 grand prix victories and 202 podiums, said at an event for Ferrari partner Puma on Tuesday night that the excitement was building.
Ferrari appointed Zhou Guanyu as a Formula One reserve driver on Wednesday after the Chinese lost his race seat with Swiss-based Sauber.
Leclerc and teammate Lewis Hamilton were eighth and 10th in the season-opener in Australia and finished fifth and sixth in China two weeks ago before both cars were disqualified for technical infringements.
'This is the most exciting period of my life, so I'm really just enjoying it and I'm so excited to get in the car tomorrow.'
Norris had shown his pace in final practice when he became the third different driver to top the timesheets in the three sessions, punching out an impressive lap 0.345 faster than anyone else.
Lewis Hamilton has expressed his total confidence in Ferrari after the Italian Formula One team's double disqualification in China.
Red Bull's Max Verstappen won the Las Vegas Grand Prix on Saturday but McLaren's Lando Norris had one hand on the Formula One title after finishing second and stretching his lead over teammate Oscar Piastri to 30 points.
Lewis Hamilton said horses were his "next thing" after riding one for the first time ahead of the US Grand Prix.
Four times World champion Max Verstappen said he had nothing to lose and would go all out to win.
Lewis Hamilton celebrated his first Formula One win for Ferrari after leading a Chinese Grand Prix sprint from start to finish in only his second race for the Italian team on Saturday.
McLaren's Oscar Piastri ended a long win drought with a pole-to-flag victory in the Qatar Grand Prix sprint race in Doha.
Norris last led the standings in April, a gap of 189 days, and had not won a race since Hungary in early August. Sunday was his sixth victory of the season, one less than Piastri, and career 10th.
Lando Norris stretched his Formula One championship lead to nine points after winning Saturday's Sao Paulo sprint while McLaren teammate and title rival Oscar Piastri crashed in a big blow to the Australian's bid to get back on top.
Formula One leader Oscar Piastri put his McLaren on pole position for the Emilia Romagna Grand Prix at Imola on Saturday
The two McLaren drivers were ruled out for excessive skid plank wear hours after the race had ended and the podium champagne been sprayed.
'Honestly, for P8 or P9 it doesn't matter. These are things we agree on internally, and this time it didn't happen.'
'Tomorrow's going to be a challenge, I've never driven this car in the rain.'
Lewis Hamilton said he was 'really enjoying' driving his Ferrari after ending the second morning of Formula One's pre-season testing in Bahrain
Verstappen wins in Qatar to ensure three-way title showdown
Lewis Hamilton smashed the Shanghai circuit lap record on his way to a stunning first sprint race pole for Ferrari in China on Friday.
Max Verstappen seized pole position for Sunday's US Grand Prix while Formula One leader Oscar Piastri qualified sixth after a costly sprint race collision with his McLaren teammate Lando Norris.
Piastri now leads Britain's Norris by 14 points with five rounds and two sprints remaining, while Verstappen has slashed his gap to the Australian to 40 after being 104 behind at the end of August.
Here's a look at some key moments which helped decide the championship fight.
Formula One will crown its champion in Abu Dhabi on Sunday with McLaren's Lando Norris and Oscar Piastri both seeking to dethrone Red Bull's Max Verstappen and deny the Dutchman his fifth title in a row.
Lewis Hamilton will launch his bid to win the drivers' championship at a third F1 team when he makes his much-anticipated debut for Ferrari in the season-opening Australian Grand Prix.
Hamilton told reporters at pre-season testing in Bahrain that he had yet to broach the subject of 'Hammer Time' with race engineer Adami.
Stewards at the Brazilian race summoned Leclerc on Friday, acting on a report from the governing FIA's media delegate and after reviewing a written transcript.
'I feel so grateful and honoured to have shared my life with such a beautiful soul, an angel and true friend.'
With eight points on offer to the winner of Saturday's 100km race, he and Norris -- 22 points behind Piastri -- both have a good chance to reduce the gap to the Australian who was three tenths slower than his teammate.
McLaren could clinch their first constructors' crown since 1998 on Sunday if they outscore Ferrari by 21 points at the Qatar F1 Grand Prix.
Lando Norris held off McLaren teammate Oscar Piastri to win the Hungarian Grand Prix on a one-stop strategy and slash the Australian's Formula One lead to nine points going into the August break.
A fired-up Max Verstappen ended his barren run as he outclassed the McLarens to register a dominant victory at the Italian Grand Prix in Monza on Sunday.
McLaren's Lando Norris edged out championship-leading teammate and Formula One title rival Oscar Piastri to take pole position for what could be a wet and chaotic Belgian Grand Prix on Sunday.