Once again, Senna took the lead while Boutsen sliced into second and Prost dropped back to fifth. However, Paolo Barilla smashed into a wall in his Minardi, blocking the track as well as bringing out the red flags.
Start No.3 was clean and Senna took the lead ahead of Berger, Prost, Boutsen, Patrese and Nannini. On lap 11, Mansell was into the pits with handling problems. He went out but retired eight laps later as the problems became serious. On lap 14, Prost sliced ahead of Berger who then pitted for tyres. Senna and Prost, separated by 2 seconds stopped at the same time but then Nannini who was planning to go without stopping came in between them. Then both Patrese and Boutsen went out with gearbox troubles. Prost passed Nannini and Berger tried the same but this time Nannini came back at him to keep the place. On lap 41, Nannini went wide and Berger sailed through to take third. Senna duly won from Prost, Berger, Nannini, Piquet and Gugelmin.
With five more races to go, Senna now had 63 points, 13 points ahead of Prost with 50. Berger was third with 33, Boutsen fourth with 27, Piquet fifth with 24, Nannini sixth with 16, Patrese seventh with 15 with Alesi eighth with 13. In the constructors, McLaren led with 96 with Ferrari second with 63, Williams third with 42 and Benetton fourth with 40.
After Belgium came Italy and Senna took pole again with Prost second, Berger third, Mansell fourth, Alesi fifth and Boutsen sixth. At the start, Berger raced past Prost while Alesi jumped by both the Ferraris. But Warwick crashed at the Parabolica, bringing out the red flags. In the restart, Berger got past Prost and Alesi got by Mansell immediately. Alesi then passed Prost into the second corner and so we had Senna leading Berger, Alesi, Prost, Mansell and Boutsen.
On lap 5, Alesi spun off and retired. Nothing changed until lap 18 when Boutsen retired with a suspension failure and Berger's tyres began to fade. Prost then passed Berger and the stops did not change anything. The top three then began to battle for the lead but none was able to close in on the other while Mansell continued to drop back, fighting a faulty throttle return spring. Senna won from Prost, Berger, Mansell, Patrese and Nakajima.
Portugal was next and the Ferraris took 1-2 in qualifying with Mansell ahead of Prost, Senna, Berger, Patrese and Piquet. At the start, Mansell's snaky start almost took Prost out and the McLarens blasted by them with Piquet getting by Prost as well. The order was: Senna, Berger, Mansell, Piquet, Prost and Boutsen.
On lap 13, Prost took Piquet for fourth and later Mansell went to the grass, allowing Prost to take third. Mansell and Berger pitted soon as Prost passed Senna at the same time to lead. These two soon pitted as well with a shuffled order: Senna, Mansell, Berger, Prost, Nannini and Piquet. The Ferraris started to close in on the McLarens in front of them by now. Behind them, Piquet passed Nannini to take fifth.
On lap 50, Mansell was close to Senna and passed him to lead. He pulled away fast but then hit Phillipe Alliot while lapping him, pushing the Ligier into a wall while Mansell got away with no damage. Prost then passed Berger on lap 59. Two laps later, Suzuki and Caffi collided and with the latter stuck in the cockpit on a zone with the wall next to the track, the race was stopped. Thus Mansell won from Senna, Prost, Berger, Piquet and Nannini.
Now in Spain and Senna took his 50th career pole position ahead of Prost, Mansell, Alesi, Berger and Patrese. At the start, Senna took off into the lead but behind them Patrese hit Alesi, spinning him into the gravel trap and into retirement. Lap 1 and Senna led Prost, Mansell, Berger, Boutsen and Patrese.
Berger was holding up a train of four cras behind him, none of them able to pass on the twisty Jerez circuit. At the stops, Mansell got ahead of Prost but waved Prost through to help his championship hopes just as Senna was coming out of the pits. He split the two Ferraris. The order was Piquet (he and Nannini were planning to go without stopping), Prost, Senna, Mansell, Nannini and Boutsen.
Prost started to attack Piquet who gave in to the pressure and went wide, dropping down to fourth. Then, Mansell attacked and passed Senna to make it a 1-2 for Ferrari as Piquet retired with battery problems. Senna pitted for tyres but retired when his radiator failed soon after. Three laps later, Berger attacked Boutsen for fourth and two collided, Berger spinning out. Prost won with Mansell making it a Ferrari 1-2 ahead of Nannini, Boutsen, Patrese and Suzuki.
With two races to go, Senna had 78 points to Prost's 69 and with both having 11 results in the points, it was clear that they would have to drop points. However, Senna would have had to drop two third places unlike Prost who would only have to drop a fourth and a fifth (if they both finish in the top 3). Berger was third with 40, Mansell was fourth with 31, Boutsen was fifth with 30, Piquet was sixth with 26, Nannini seventh with 21 and Patrese eighth with 19. In the constructors, McLaren led with 118 points with Ferrari second with 100. Williams was third with 49 and Benetton was fourth with 47.
Before the Japanese Grand Prix, Nannini was involved in a helicopter crash and sustained career-ending injuries (though he would later return to touring car racing). He was replaced by Roberto Moreno for the rest of the season. Moreno had been free since EuroBrun had withdrawn from Formula One, along with Life. As a result, pre-qualifying was not needed.
In qualifying, Senna took pole ahead of Prost, Mansell, Berger, Boutsen and Piquet. However, Senna was unhappy at the side the pole was on as the pole was on the dirty side of the track and thus the second place being on the racing line which should give the second-placed driver the advantage into the first corner. He went to FISA president Jean Marie Balestre to change the side where the pole was, but was refused. After this, he decided that he would go for any gap into the first corner if Prost had the advantage. At the start, Prost did have the advantage and Senna went for the gap. Prost did not know it and closed the door. Senna's left front touched Prost's rear wing, spinning both of them into the gravel trap. The world championship was sealed.
Although Senna led by 9 points and there were 9 points for a win, if Prost won the last race he would have had to drop his fifth place in Canada which meant that he would be two points behind Senna even if Senna retired. Senna was the new world champion. Back to the race now and Berger was leading Mansell, Piquet, Moreno, Boutsen and Patrese. At the start of the second lap, Berger spun off into retirement after hitting debris from the Senna-Prost collision. This left Mansell who was under pressure by the Benettons leading.
Mansell then began to pull away from Piquet and Moreno as Suzuki passed Warwick for sixth. Mansell pitted with a 15-second lead on lap 27 for tyres but his driveshaft snapped as he went out of his garage. He retired giving the Constructors title to McLaren as they were 18 points ahead and a 1-2 can get only 15 points. The Benettons and Suzuki did not stop but Patrese and Boutsen did with Patrese getting ahead at the stops but both rejoined behind Suzuki. Then Nakajima passed Warwick to take sixth as Warwick then retired with gearbox trouble. Piquet won with Moreno making it a Benetton 1-2. Suzuki was third, Patrese fourth, Boutsen fifth and Nakajima sixth.
The last race of the year was in Australia and the McLarens took 1-2 in qualifying ahead of the Ferraris, Senna ahead of Berger, Mansell, Prost, Alesi and Patrese. At the start, Senna took off into the lead with Berger defending from the Ferraris and Piquet getting by Alesi and Patrese. The order was: Senna, Berger, Mansell, Prost, Piquet and Alesi.