The monocoque made the car more rigid and structurally stronger than typical F1 cars of the period. The 25 was three times stiffer than the interim 21, while the chassis weighed only half as much.As a result, the car was extremely low and narrow (frontal area only 8.0 ft², 0.74m² compared to the normal 9.5 ft², 0.88 m²)It was also envisaged to have a column gear lever, to keep cockpit width to a minimum, although this was only experimental and discarded. To assist this, the driver reclined sharply behind the wheel (an idea seen in the 18, and pioneered over a decade previously by Gustav Baumm at NSU), leading to the nickname 'The Bathtub', while front suspension pieces were moved inboard (as in the 1948 Maserati).The 25 was powered by a 1498cc Coventry Climax FWMV V8, although Reg Parnell Racing in 1964 fitted BRM P56s of similar specification to their second-hand 25s. Such was 25's effect on motor racing, even today's modern F1 cars follow its basic principles.
Some privateers who had been buying Lotus chassis were disgruntled by the fact Chapman refused to provide them 25s. These teams, including Rob Walker Racing, were given Lotus 24s, while the works team had exclusive use of the 25 for Jim Clark and Trevor Taylor. When it first appeared at the Dutch Grand Prix, the futuristic 25 was inspected by John Cooper, who asked Chapman where he had put the chassis in the car.
The car gave Clark his first Grand Prix victory, at Spa, that year. He followed by taking another win in Britain, and again in the USA, which put him in contention for the title, but at the final race, South Africa while leading, a much publicised engine seizure cost him the title to Graham Hill.
Clark gained his revenge the following year, taking his first world championship in the 25, by winning 7 races, Belgium, France, Holland, Britain, Italy, South Africa, and Mexico. Lotus also won its first constructors' championship. In addition, 25s were entered at Indianapolis, where they trialled Lucas electronic ignition for Ford. The 25 was used during the 1964 season, winning a further three races in Clark's hands. At the final race in Mexico, just as in 1962, the Climax engine developed an oil leak and with literally a lap to run Clark coasted to a halt in sight of world championship victory, this time conceding to John Surtees.
Clark went on to take the car's final win at the 1965 French Grand Prix before it was replaced by the Lotus 33. The Lotus 25 won 14 races, took 17 pole positions, and set 13 fastest laps.
In 2008/9 Lotus launched a special edition of the Elise supercharged model in the original Lotus 25 racing colours. This had track standard sports suspension and traction control. A total of 25 of these Lotus Jim Clark Type 25 cars were produced for the RHD market.