Today's Samsung Mobile 500 at Texas Motor Speedway could provide an answer.
Today's race (3 p.m., ET, Fox-Ch. 54) is the third race for the traditional spoiler across the trunk deck, but it's the first for a track where speeds approach 200 mph. With so much effort being made to improve side-by-side racing, there is a lot riding on it.
"I think no matter what happens here, there's going to be a verdict on the spoiler," Jeff Burton said. "... I think that no matter what happens from here, if we have a great race, if we have a poor race, there's going to be a determination that the spoiler was really good or the spoiler was really bad."
The spoiler returned in March at Martinsville Speedway, the slowest track on the Sprint Cup Series schedule. Last week's race at Phoenix International Raceway was a flat, one-mile oval where the spoiler had little consequence.
At 1.5 miles, Texas is different. Cars in today's race will need all the traction a rear spoiler can provide, especially in turbulent air created by traffic. If cars are unstable in traffic -- something that was common with the rear wing -- then long runs of follow-the-leader racing will continue.
"I think the biggest challenge is going to be in traffic and seeing how this car with the spoiler reacts in traffic," Jeff Gordon said. "This, to me, is the biggest test of them all."
Rain washed out both practice sessions on Saturday.
Reach Don Coble at firstname.lastname@example.org.