| Rank | Driver | Team | Speed |
| 1. | Kyle Larson | Chip Ganassi Racing | 188.403 |
| 2. | William Byron | Hendrick Motorsports | 188.298 |
| 3. | Ryan Newman | Richard Childress Racing | 188.186 |
| 4. | Kurt Busch | Stewart-Haas Racing | 187.846 |
| 5. | Erik Jones | Joe Gibbs Racing | 186.722 |
| 6. | Brad Keselowski | Team Penske | 186.574 |
| 7. | Ricky Stenhouse Jr. | Roush Fenway Racing | 186.245 |
| 8. | Kasey Kahne | Leavine Family Racing | 186.200 |
| 9. | Darrell Wallace Jr. | Richard Petty Motorsports | 185.970 |
| 10. | Paul Menard | Wood Brothers Racing | 185.701 |
| 11. | Chris Buescher | JTG Daugherty Racing | 185.631 |
| 12. | Ty Dillon | Germain Racing | 185.052 |
| 13. | Drew Herring | Toyota Wheel Force | 184.887 |
| 14. | Cole Custer | Go Fas Racing | 184.225 |
| 15. | Justin Allgaier | Chevrolet Wheel Force | 182.761 |
| 16. | David Ragan | Ford Wheel Force | 181.971 |
Byron, Larson lead Las Vegas test sessions
David Becker | Getty Images
William Byron of Hendrick Motorsports and Kyle Larson of Chip Ganassi Racing led the morning and afternoon sessions, respectively, during open testing Wednesday at Las Vegas Motor Speedway.
Byron's top speed of 188.298 mph was good enough to beat out Ryan Newman, who was second at 188.186 mph for Richard Childress Racing. Stewart-Haas Racing's Kurt Busch, Larson and Joe Gibbs Racing's Erik Jones rounded out the top five during the morning session. Full results are at the bottom of this story.
RELATED: Behind the scenes at Las Vegas test
In the afternoon session, Larson led with a top speed of 188.403 mph, which held up as the top speed of the day. Newman again finished second (187.162 mph) with Byron, Kurt Busch and Jones rounding out the top five. Sixteen drivers tested Wednesday on the 1.5-mile track, site of the third Monster Energy NASCAR Cup Series race of the 2018 season and the NASCAR Playoff opener in September.
The test concludes tomorrow after another round of practices.
Wednesday was also the first time for some drivers of the Chevrolet Camaro ZL1 to try out the new model on the track.
“It’s nice to get back in a stock car," Larson said. "I’ve still done a fair bit of racing this offseason. But it's been a couple of months since I've been in a (stock) car. It was nice to get some laps here and feel like we've got some pretty good speed and good balance with our new Camaro ZL1."