The Lotus 33's development was based on the earlier Lotus 25 model, taking the monocoque chassis design to new development heights. The 33 was again powered by the 1500 cc Climax engine. The 33 was almost identical to the 25, but had suspension designed around newer, wider tyres. The car was more rigid and was simpler to build than its predecessor.
Five Lotus 33s were constructed, with chassis numbers following on from the 25. Another chassis, serial number 'R12', was modified to take the stillborn Climax flat-16 engine; this car was designated the Lotus 39. Serial number 'R13' was not used by Team Lotus but was later adopted by Reg Parnell Racing for their rebuilt Lotus 25.
Introduced for the 1964 season, the 33 made its first appearance at the non-Championship Aintree 200. Clark qualified fourth, and set fastest lap before retiring. The 33's first World Championship event was the German Grand Prix. However, both Clark and his team mate Mike Spence struggled with the car and it was not until the following year that it came good. Clark won the first event of 1965, the South African Grand Prix and went on to take four more wins on the way to his second world championship. Clark missed the Monaco Grand Prix (a race which he would never win) to race in the Indianapolis 500, which he won.
In 1965 a four-valve version of the Climax engine was used which had an increase in power (about 210 bhp (157 kW) - 220 bhp (164 kW) compared to the older Climaxes which gave about 200 bhp). However the extra power sacrificed reliability, and Clark retired from the final 3 races of 1965, fortunately after he'd wrapped up the title. The 33 was pressed into service with bored out 2 litre Climax V8 and BRM V8 engines for the early races of 1966, until the 3 litre Lotus 43 was ready. In 1967, with the new Lotus 49 still suffering teething trouble, the 33s were deemed more suitable for the tight turns of Monte Carlo. Clark set fastest lap but retired his Climax-engined 33 while Hill drove the BRM-engined car to second place.
1 Points were awarded on a 9-6-4-3-2-1 basis to the first six finishers at each round, but only the best placed car for each make was eligible to score points. In 1964 and 1965 only the best six results from the season were retained, and only the best five results for 1966. In 1967 the best five results from the first six rounds and the best four results from the last five rounds were retained.
2 Total points scored by all Lotus-Climax cars, including Lotus 25 variants.
3 Total points scored by all Lotus-BRM cars, including Lotus 43 variants.