While NASCAR's new race car, the Gen-6, continues to be a work in progress, it is showing signs of improvements based on its performance in Sunday's race at Las Vegas Motor Speedway.

The car didn't get rave reviews from all after the Daytona 500 on Feb. 24 and then one week later at Phoenix International Raceway. Some drivers complained it was too hard to pass, and there had been a lack of side-by-side racing.

Denny Hamlin was the most outspoken, and his comments about the car landed him into trouble with NASCAR. Hamlin compared the Gen-6 with the previous race car, the fifth generation vehicle, which was commonly referred to as the Car of Tomorrow (COT) when it made its debut in 2007.

When Hamlin was asked about his opinion of the car after he finished third at Phoenix, he replied, "I don't want to be the pessimist, but it did not race as good as our generation five cars. This is more like what the generation five was at the beginning. The teams hadn't figured out how to get the aero balance right. Right now, you just run single-file, and you cannot get around the guy in front of you. If you would have placed me in 20th place with 30 (laps) to go, I would have stayed there. I wouldn't have moved up. It's just one of those things where track position is everything."

NASCAR slapped Hamlin with a $25,000 fine after the sanctioning body determined he made "some disparaging remarks" about the car.

To better understand the Gen-6 for its first race at a 1.5-mile track, NASCAR gave teams a full day of testing at Las Vegas on Thursday. It was a good thing for an extra day of practice since all track activities were canceled on Friday due to rain.

The Gen-6 cars -- Chevrolet SS, Ford Fusion and Toyota Camry -- are not only faster than the ones from the previous generation but have more downforce and better grip. The 400-mile event at Las Vegas was the next big test for the Gen-6, and it seemed to earn a better grade than it did for the first two races this season.

"It was a really interesting race from my seat," said Las Vegas winner Matt Kenseth. "The pace was fast. There was one run where I was pretty darn happy with the car. I thought it was a really entertaining race. I was watching Kyle (Busch) run up there and get the lead, and then Kasey (Kahne) would be better in the long runs. He would start working a different groove. I thought it was interesting."

The Las Vegas race, which featured 22 lead changes among eight drivers and ran at a pace of 146.287 mph, had its share of passing as well as two-wide and sometimes three-wide racing, particularly after a restart. Kenseth gambled on tires late in the race and then held off a fierce challenge from Kahne in the closing laps to win on the same day he turned 41 years old. Kenseth, who pitted for fuel only during the last round of stops with 42 laps to go, beat Kahne to the finish line by 0.6 seconds.

Kahne had a dominant car, leading 114 of 267 laps.

"My car drove good," he said. "I felt like I could pass. I could race underneath the car and do things that maybe I wouldn't have been able to do in the past. First time on a mile and a half with this new Gen-6 car, and I would say to have the same tires -- this is the same tire, also, which we didn't have last week, which was a big part of the Phoenix deal.

"I had a lot of fun driving it, and I thought it was a heck of a race. I got to race through cars, traffic and battle for the lead four, five, six times."

All three automobile manufactures in the Sprint Cup Series have gone to victory lane this season. Jimmie Johnson won the Daytona 500 in a Chevrolet. Carl Edwards drove his Ford to victory at Phoenix. Kenseth gave Toyota its 50th win in Sprint Cup at Las Vegas.

The Gen-6 will be a big topic again this coming weekend. Bristol Motor Speedway is the first short-track race for the car. It's likely that we'll see a different type of racing at this famed half-mile track.

"I think short track racing is going to be short track racing," Johnson said. "The bumpers aren't as square, so the bump-and-run can be far more effective. It was really tough to get somebody out of the way with the COT, or Gen-5 car, so we might see a little difference there. I think the crash damage is going to be different."

After Bristol, the series heads out west again to the two-mile Auto Club Speedway in Fontana, Calif.