FONTANA, Calif. – Hendrick Motorsports driver William Byron wrapped up the fourth test of NASCAR’s Next Gen race car on Tuesday afternoon at Auto Club Speedway.

Byron is the fourth different driver to test NASCAR’s Next Gen race car, which will debut next season. Austin Dillon, Joey Logano and Erik Jones have tested the car during previous on-track testing at Richmond Raceway (Dillon), Phoenix Raceway (Logano) and Homestead-Miami Speedway (Jones).

“I was definitely excited about the opportunity to test this car and see how it drives,” Byron said. “Auto Club Speedway is a really great track to test, especially since we just raced here. I talked to Erik (Jones) beforehand and he mentioned a few things about how it drove – how the steering was different, things like that.”

According to a NASCAR.com story, the car Byron tested is the third prototype in the developmental process of the new car. This version of the Next Gen car is considered almost 100 percent compete ahead of its debut in the 2021 Daytona 500.

“This is a brand-new car. We didn’t take any parts off the car we had at Richmond, Phoenix and Homestead,” said John Probst, NASCAR Senior Vice President of Racing Innovation. “Our goal was to take all the feedback we received from the first three tests and implement that into what we consider our pre-production prototype. This is what we intend to race in 2021. What you see here today is a result of all the testing and input we’ve received.”

“I was really curious to see what would be different on this car,” Byron said. “Our current car has kind of been maxed out in terms of what we can do with it. It’s going to take some time to learn this car, so we have to be patient and see how things go. We’re just trying to learn as much as we can right now during this test.

“I’ve been happy with it, especially as we’ve been adjusting it more and tailoring it to this track – this is the biggest track it’s been on so far. As soon as it started to go for us, I thought the steering felt better and the car felt more stable. It’s been fun the more laps I’ve been able to run.”

Everything didn’t go perfectly during the test, as Byron’s Tuesday session was cut short following an incident during a 25-lap run.

“We were probably six or seven laps into a 25-lap tire run. I had been a little free for a couple of corners, but nothing major,” Byron said. “That time, I just got loose and figured I’d be able to save it but wasn’t able to. It just came all the way around. I had a number of similar moments in the race Sunday and was able to drive out of it. That’s what caught me off guard the most. It’s part of testing though, learning where the line is with what the car can do.”

The test also marked the debut of the 18-inch, single center-locking lug nut on the wheels of the Next Gen car.