SONOMA, Calif. -- The thermometer hovered at 102 degrees just prior to Friday's qualifying at Infineon Raceway, which means the temperature inside the Sprint Cup cars was much hotter.
Not to worry.
NASCAR is monitoring the situation.
The governing body began last week at Michigan International Speedway monitoring the heat inside the new cars after several drivers complained that they were hotter than the old cars.
They also began doing random tests for carbon monoxide to guarantee nobody was at risk.
The findings were just what officials anticipated, that cars with proper ventilation, vents and insulation had no problem. For example, the temperature inside the car of Brian Vickers was 130 degrees, compared to 105 for another.
"You start looking at the cars and say how can this be, they're all the same?" series director John Darby said. "Well, the 105 degree car didn't have a lot of vents and stuff in it, but they did take the time to insulate the floorboard and put insulation around the exhaust pipes.
"There's so many little things that make a difference that if you want to do them you can do them."
Monitoring the heat isn't new to NASCAR. Darby said the governing body periodically has done this for six years when the temperatures are unusually hot or "you get a couple of guys whining about it."
He said temperatures have gotten as high as 148 degrees with the old car.
Vickers and Denny Hamlin whined about the heat two weeks ago at Pocono, saying the new cars were much hotter than the older ones. Hamlin's team made adjustments, adding vents to allow in more outside air at Michigan.
"When I got out of the car my [carbon monoxide] level was zero at Michigan," Hamlin said. "We improved as a team and I felt a whole lot better."
Kevin Harvick said heat inside the car began going up last season when NASCAR switched to unleaded fuel. He agreed that the solution is more on the teams than blaming the new car.
"There's definitely things to make the insides of the cars safer," he said.
That NASCAR is monitoring the situation, whether it's needed or not, is welcome to most drivers.
"It's good that drivers can say, 'Hey, we're having this issue," and NASCAR tries to help with it," Jeff Burton said. "They are hot. There's no question the cars are hotter than they used to be. I also believe from a carbon monoxide level personally I'm at an all-time low of carbon monoxide exposure."
Darby said none of the eight to 10 drivers tested for carbon monoxide at Michigan showed a dangerous level.
Carl Edwards said the CO level concerns him more than the heat, which he never believed to be a problem.
"I would assume it's the CO and not the heat," he said. "I don't have a cool box. I have an old style seat and I'm not too hot."
Four-time Cup champion Jeff Gordon is being just as pro-active as NASCAR, adding a workout program with a mountain bike to his routine to help handle the heat and the tougher handling problems the new car presents.
"I'm working harder with this car," he said. "This car is challenging on the teams and the drivers. I'm trying to step up my game as well knowing I'm going to be working harder and it's going to be hot. I want to make sure I'm not leaving anything out there on the table."
David Newton covers NASCAR for ESPN.com. He can be reached at firstname.lastname@example.org.