Mark Webber says Fernando Alonso's plan of dovetailing a Le Mans effort with his F1 commitment is a mistake given the specific requirements of the endurance classic.
In his quest for motorsport's Triple crown - or winning the Monaco Grand Prix, the Indy 500 and Le Mans - Alonso is expected to race in the legendary 24-hour event this year with Toyota.
But Webber, who successfully transitioned from F1 to the World Endurance Championship with Porsche in 2014, believes a proper onslaught at Le Mans requires total dedication and an exclusive focus, two requirement he feels his friend will have difficulty fulfilling as long as he remains in F1.
"It's a mistake, they are two totally different things," Webber told Italian website Automoto.it, as he explained the differences between F1 and Le Mans.
"They both absorb a very high amount of mental energy," he added.
"If you do Formula 1 you cannot afford certain distractions. I say this after doing several seasons and racing at Le Mans. If I were Fernando, I wouldn't do it."
Webber believes the talented McLaren man, who will race at Daytona at the end of the month, should have no difficulties adapting to a different environment, despite the specifics linked to endurance racing.
However, the Aussie would not recommend racing at Le Mans with limited preparation and other things going on in the background.
"Either he chooses to do Le Mans properly and focuses on it, working on it three weeks in advance with a maniacal focus and forgetting the rest of the year, or he could risk getting hurt.
"At Le Mans, it all starts days before the race," Webber explains.
"You run in the day, then in the night, then you've got the parade downtown with the fans, the meetings with the engineers, how the race will be divided up with your team mates, how to hand over the car to them without losing any time, and vice versa.
"It requires a very strong mental commitment, and to understand if it's all worth it, I think Alonso is right to do Daytona," insists Webber.
"He'll assess everything and get an understanding of what is needed. And then I'm sure he'll take the right decision."
Nico Hulkenberg won Le Mans in 2015 while racing full time in F1 with Force India, but Webber believes triumph was achieved in an entirely different context.
"That was with a second-rate team in F1. The pressures are different," says Aussie Grit.
"He was also with the top Le Mans team and that simplified things a lot."