The Renault Formula 1 braking system deemed illegal by the FIA was in use as early as the 2015 Belgian Grand Prix when the team was Lotus, claims Romain Grosjean.
Renault was disqualified from the Japanese Grand Prix for using the system - a pre-set brake balance adjustment, which it admitted was a driver aid.
Team boss Cyril Abiteboul revealed the device had been used "for a while" but would not confirm how long, beyond admitting it was in operation before 2019.
Grosjean drove for Lotus in 2015 - the final season before it became Renault again - alongside Pastor Maldonado, but moved to Haas the following year.
Asked if he had mentioned on Thursday at the Mexican Grand Prix that he drove with the system since the Spa round in 2015, in which he scored a podium, Grosjean said: "I may have. Yes."
Grosjean was then asked whether he considered the device to be legal, and responded: "Well let's say that I asked to replicate it later on and they wouldn't do it.
"It was good though."
Racing Point challenged the braking system after the Japanese GP, and said it had done so because the FIA confirmed it was not allowed to replicate the system.
Abiteboul said Renault had not sought approval from the FIA for the design because it was convinced it was legal given how long it had been on the car.
He also stressed it was not a performance-enhancing driver aid, simply a way to reduce the driver's workload.
However, Racing Point driver Lance Stroll thought there will have been a benefit.
"They [the FIA] clearly gave them a penalty because it was an advantage," he said.
"However, I don't know the ins and outs of it, or how much they were doing it, or how much lap time it was, how much pace they were finding because of it.
"But I definitely know that they gave them a penalty for a reason.
"There is definitely a lot of workload for the driver, changing brake balance throughout a grand prix, and if you can avoid that, it's definitely helpful."