In the 2021 season Rahal Letterman Lanigan Racing again expanded to three cars, with Graham Rahal and Takuma Sato driving two full-time entries while several drivers would drive a third car on a part-time basis. Sato in his #30 car sponsored by Shield Cleansers, an American cleansers and protection equipment company, achieved his best season at first round of the Detroit Grand Prix where he was 4th. Sato ultimately finished 11th in the championship.
|Takuma Sato||30||Rahal Letterman Lanigan Racing|
|Dallara DW12 (IR18)||Honda||Panasonic / Shield Cleansers|