The Type 33 made its debut at the 1964 German Grand Prix.
This was basically a 25 with 13” wheels, a longer wheelbase and improved suspension.
There were initial reliability problems, though the end of the season saw a 6th place for Mike Spence in the Italian Grand Prix and a 5th place for Walt Hansgen in the US Grand Prix.

Introducing the 33 in 1964 paid dividends the following season (the last with 1.5 litre engines).
Clark won 5 races in the 33, with Mike Spence having a good season with 3 points scoring finishes.

Clark won the drivers title with 54 points.
Spence finished in equal 8th with 10 points.
Lotus again took the Constructors Title.

1966’s new engine regulations saw many teams unprepared for the season.
Coventry-Climax had withdrawn from Formula One, leaving Lotus without an engine supplier.
BRM units were used as a stopgap.

Jim Clark continued to use the Coventry-Climax engine in his 33 for the first 6 races, but only bagged 7 points before changing to a BRM powered Type 43 for the last 3 races of the season.

Mike Spence used BRM power for all but the last two races in his Type 33, but only scored 4 points form two 5th places.

Peter Arundell also drove for Team Lotus in 1966 and scored 1 point in the US Grand Prix with a Coventry-Climax powered 33.

The last major success for the 33 was 2nd place in the 1967 Monaco Grand Prix.