The FW12 emerged following a successful period for Williams, having won both the Constructors' and Drivers' Championships in 1986 and 1987 with the Honda-powered FW11 and FW11B. However, a breakdown in the relationship with Honda—stemming from disagreements over driver selection and the perceived treatment of Nelson Piquet—led to the Japanese manufacturer announcing a switch to McLaren for 1988. This left Williams seeking a new engine supplier, ultimately settling on Judd for the 1988 season. The FW12 was designed to accommodate this change, moving away from the V6 turbo engine to a naturally aspirated V8.
In its original form, the FW12 was powered by a Judd CV 3.5 V8 engine. Williams also continued development of their computer-controlled "active suspension" system, initially debuted on the FW11 at the 1987 Italian Grand Prix (branded "Williams Reactive Ride" to avoid copyright issues with Lotus’s “Active Suspension” name). The team revised the system for the FW12, hoping it would provide an advantage, but these revisions proved problematic. The system added approximately 25 kg (55 lb) of weight and consumed around 5% of the engine’s power, a manageable trade-off with the powerful Honda V6. However, with the less powerful Judd V8—producing around 600 bhp (447 kW; 608 PS) in its first year of F1 competition—the system’s parasitic losses were more significant. The car was described as being “pathetically slow in a straight line,” recording speeds of only 265 km/h (165 mph) at the Brazilian Grand Prix, compared to over 290 km/h (180 mph) achieved by McLaren and Lotus with their Honda turbo engines.
The 1988 season proved difficult for Williams with the FW12. Both Nigel Mansell and Riccardo Patrese described the car as slow, and the reactive suspension system caused unpredictable handling due to air entering the hydraulics. Mansell failed to finish the first seven races of the season, and the team only scored one point before the British Grand Prix. At Silverstone), Technical Director Patrick Head made a significant change, replacing the reactive suspension with a conventional system. Head described this as a “bodge job done on the fly” . Both drivers immediately noticed an improvement, with Mansell improving his qualifying time by 1.3 seconds and Patrese by 17.864 seconds. Mansell subsequently finished second in the British Grand Prix, setting the fastest lap of the race.
Mansell missed the Belgian and Italian Grands Prix due to chickenpox, being substituted by Martin Brundle and Jean-Louis Schlesser respectively. Schlesser’s single World Championship F1 race ended with a collision with race leader Ayrton Senna at Monza, ultimately costing Senna the race and handing a 1-2 finish to Ferrari. The FW12 showed improved competitiveness towards the end of the 1988 season, with Mansell finishing second in Spain.
For the 1989 season, Williams partnered with Renault, developing the RS1 3.5 V10 engine and creating a test mule, the FW12B, to accommodate its larger dimensions. The updated FW12C debuted in 1989, achieving a promising start with Patrese qualifying second in Brazil and leading the race before a mechanical failure. Thierry Boutsen, who replaced Mansell, secured the car’s only win at the rain-affected Canadian Grand Prix, with Patrese finishing second for a 1-2 finish. Patrese also achieved the car’s only pole position at the Hungarian Grand Prix, leading the race until a radiator issue forced his retirement.
As the 1989 season progressed, it became apparent that the FW12C had reached its development limit, falling behind McLaren and Ferrari. Williams decided to focus on its successor, the FW13, and retired the FW12C after the Italian Grand Prix, though Patrese briefly reverted to the FW12C for the Spanish Grand Prix. The FW12C’s final race appearance was at the Spanish Grand Prix, where Patrese finished fifth.
The Williams FW12 and FW12C scored 1 win, 1 pole position, 2 fastest laps, and 9 podium finishes in their 29 races. The experience gained with the Renault V10 engine and the development work on the FW12C directly informed the design of the FW13. James Hunt test drove the FW12C in December 1989.