NASCAR’s long-awaited return to the international stage, its first in 67 years since the 1958 race in Canada, has arrived in Mexico City with a fresh set of hurdles for teams and drivers alike. From soaked asphalt ahead of practice and qualifying sessions to an unusual pit road positioned on the right-hand side, and the added complexity of racing at high altitude, the debut at Autódromo Hermanos Rodríguez is shaping up to be anything but routine.
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Situated nearly 7,500 feet above sea level, the iconic circuit presents a dual-threat challenge. Thinner air at altitude not only affects driver stamina and physical response but also takes a toll on the engines, with reduced oxygen impacting horsepower and cooling.
To combat the physiological strain, drivers have turned to a variety of altitude training methods, including arriving early to acclimate, wearing oxygen-restrictive masks, and even sleeping in hypoxic tents to simulate high-altitude environments.
Mechanical challenges, however, require a different playbook. In response, NASCAR has given Chevrolet, Ford, and Toyota the green light to make a key adjustment following Friday’s practice: each manufacturer may opt to run an alternate hood louver for the remainder of the weekend. But the catch is that teams must make a unified call across their respective entries, with no mix-and-match setups allowed.
Joe Gibbs Racing competition director Chris Gabehart broke down the logic behind the move. “Think about the amount of air density you’re passing across the radiator and into the engine. It uses those molecules of air to do the work. Up here, you’re going the same speed, so you don’t get any more speed to get more air, but the air is a lot thinner.”
“So now I just have less air to do the cooling or to feed the engine horsepower — all those things. So, the only way to get more out of it is to get the whole system to pass more air across the radiator.”
The alternative louvers offer increased airflow to help manage engine temperatures, but at the cost of aerodynamic efficiency, specifically, a dip in downforce.
Ford, Chevrolet and Toyota have a significant decision to make for each of their teams after practice in Mexico City on Friday
And the verdict appears to be two different directions across the three. https://t.co/MylIpIgYSg
— Matt Weaver (@MattWeaverRA) June 14, 2025
Hyak Motorsports competition director Mike Kelley elaborated on the tradeoff. He noted that using open louvers means teams can’t simultaneously run a blocker plate, which typically helps manage airflow through the grille.
So, there’s a little downforce loss and drag gain if a team does that, but it’s the right way for NASCAR teams to go right now because the temperature is going to be too high the other way.
In essence, giving up a sliver of aerodynamic sharpness may be the only path to survival in the thin air of Mexico City. Following practice, Kelley confirmed that Chevrolet teams would run with both the louvers open and the blocker plates out.
However, Hendrick Motorsports vice president of competition Chad Knaus stopped short of locking in that direction for his group, saying, “It probably looks that way,” but added the team hadn’t “circled up 100 percent yet to make that decision.”
As the teams adapt to an unfamiliar venue, elevated conditions, and unprecedented choices, the Mexico City weekend is already testing the Cup field in ways few anticipated.
