The Benetton Group's purchase of Toleman was only finalised in October 1985, leaving the design team precious little time before the opening race of the 1986 season. Chief engineer Rory Byrne did not begin work on the car until the engine-supply deal with BMW was confirmed in the last week of that month. Despite the tight timeline, three cars were ready for the Brazilian Grand Prix on 23 March 1986, and a further four chassis were completed during the season.
The organisational structure of the former Toleman outfit remained largely intact under Benetton ownership. Peter Collins continued as team manager, Byrne stayed as chief engineer, and the team remained headquartered at its Witney base in England. The key difference was the arrival of BMW engines, replacing the privateer Hart 415T units that had powered Toleman since the team's 1981 Formula One debut. Benetton received the standard upright version of the BMW M12/13 inline-four turbocharged engine, while the radical new lay-down variant was reserved for the Brabham BT55.
The chassis was refined from its predecessor with reshaped sidepods for improved aerodynamic downforce and additional structural reinforcement to handle the enormous stress imposed by the BMW engine. The cockpit design presented a notable challenge: accommodating both the compact Teo Fabi, around 1.68 metres tall, and Gerhard Berger, who stood 1.83 metres.
The BMW M12/13 engine supplied to Benetton was, in qualifying configuration, one of the most powerful units in Formula One history. Modified engine management chips gave the Benetton-spec engines approximately 50 bhp more than the factory Brabham units, with qualifying outputs reportedly reaching around 1,400 bhp at approximately 4.5 bar of boost. Race trim figures were closer to 900 bhp. At Monza, Berger recorded a season-fastest top speed of 352 km/h through the speed trap, and Benetton occupied four of the five fastest slots through the traps at that event. BMW-powered cars had the most powerful engines in the field, although the raw pace did not always translate into results due to turbo lag on slower circuits and significant fuel consumption challenges.
The B186 scored points in its first three outings, including a podium for Berger at the San Marino Grand Prix. Development gathered pace through the year as aerodynamic packages were progressively updated with revised front and rear wings, underbody changes, and new suspension geometries. A significant step came at the Austrian Grand Prix at the Österreichring, where improved aerodynamics and the high-speed layout produced a dominant qualifying lockout with Fabi on pole and Berger alongside. A likely one-two finish unravelled when Fabi over-revved his engine after a kerb ride and Berger lost five laps to a battery change.
The season culminated at the Mexican Grand Prix, the penultimate round, where Berger converted pace into Benetton's maiden Formula One victory. The key factor was tyre strategy: Berger's Pirelli rubber proved sufficiently durable that he required no pit stop, while rivals including Nelson Piquet, Alain Prost, and Nigel Mansell lost time to stops or mechanical issues. The win validated Berger's emerging talent, Benetton's first season as a constructor, and the competitiveness of the BMW-Pirelli combination when conditions aligned. The Mexican race was also the final Formula One victory for the BMW M12/13 engine.
Pirelli's relative durability compared to Goodyear-shod rivals proved a recurring advantage in the second half of the season, partially offsetting the Italian tyre manufacturer's slower pace in the year's early rounds. Total retirements across the season numbered nineteen from 32 starts, underscoring the chassis's underlying unreliability under the BMW engine's extreme power output.
The B186 established Benetton as a credible Formula One constructor from its very first season. Despite entering the year under significant time pressure and with a driver pairing of contrasting statures and styles, the team extracted a victory and confirmed the latent competitiveness of the design. Gerhard Berger's win in Mexico was the first of ten career victories, a result that positioned him as one of the era's top drivers. The B186 was succeeded by the Ford turbocharged B187 for 1987, marking the end of Benetton's association with BMW and Pirelli at a stroke.