NASCAR kicked off its final test of the year on Tuesday at Charlotte Motor Speedway as teams continue to prepare the sixth-generation Sprint Cup cars for the 2013 season.

Sixteen drivers representing 10 Cup teams participated in the test session that ran from 9:45 a.m. to 5 p.m. (ET). Casey Mears, driver of the No. 13 Ford, was the first to hit the track this morning.

For some of the drivers it was their first time driving the Gen-6 car, including Dale Earnhardt Jr.

"I’m really impressed," Earnhardt Jr. said after driving the Chevrolet SS for the first time. "I really like the balance of the car, the downforce seems to be relatively good. The car has driven well for us today. We will just move through the next couple of days here and keep tuning. Trying things and see what the car likes and doesn’t like. A lot of the rules and decisions that NASCAR is going to make on this car, some are finalized, some are not. It’s still a little bit of a moving target for the teams."

Earnhardt said that the new car reminds of him of the racecar prior to the switch over to the COT-style full time in 2008. Before to the move to the COT, Earnhardt Jr. won 17 of his 19 career Cup races.

"I like it already leaps and bounds beyond the COT or the old car we ran," Earnhardt Jr. said. "This car really gives me a lot of sensations that are similar to the old car that we ran four years ago or however long ago it was. It’s still early. I’m trying not to get too excited or form too big of an opinion or too solid of an opinion of the car. We have got a lot of things to learn about it. There are still some rules and things to be finalized and still a lot to learn."

Along with the new body on the car behaving better aerodynamically, Earnhardt felt an increase in grip due to more camber in the rear end of the car.

“The rear camber is a big deal," Earnhardt said. "I do know that it’s going to provide a ton of grip being able to camber the right-rear tire any more than we had in the past. I know that is a big advantage to adding grip to the car."

One thing that Earnhardt noticed inside the car was the view out the rear window and the new 7 1/4-inch spoiler.

"We have a gigantic rear spoiler on the car," Earnhardt Jr. said. "You can’t see out of the car very well, but that spoiler is doing a lot. NASCAR seems to think that spoiler is the one that is going to provide the better package for better racing. It definitely gives the car a lot more comfort and it does resemble what we ran many years ago. Those were some pretty good race cars back then."

Just 12 days after celebrating the championship in Las Vegas, Brad Keselowski was back on track, but this time in a Ford as his Penske Racing team made the switch from Dodge at the end of the season.

“It’s hard to get a great read on the whole manufacturer change because, obviously, it’s a different car, but I think all the signs are there that we have the potential to be just as strong, if not stronger, than we were last year, which is very, very encouraging," Keselowski said. "We still have to work for it and make it happen, but the signs are there."

Today's test session gave Keselowski time to work with his new teammate Joey Logano.

"It’s been a lot of fun having the first day today working with Joey, which I think has been probably more of an adjusting process than the actual car itself, and a good adjusting process. I’m curious to see over time how we can work together and push each other to be the best we can be, so I’ve had a lot of fun with that so far."

Both Penske cars were sporting their 2013 paint schemes in the test with Logano in the Shell-Pennzoil colors in his first run with the team and crew chief Todd Gordon.

"It's all gone really well," Logano said. "I'm very pleased with the way the car has been driving. Todd and I are working good together and the yellow and red looks pretty good."

Matt Kenseth was another driver who made a move to a new team in the offseason and was testing the Joe Gibbs Racing No. 20 Toyota that Logano occupied for the past four seasons. (Read More on Kenseth).

The morning session basically consisted of single car runs with Jeff Burton topping the speed chart at 190.833 mph in his No. 31 Chevrolet. The afternoon session saw cars go out in a large pack to try and simulate race conditions. Regan Smith, who is testing the No. 24 Chevrolet for Jeff Gordon, was the fastest in the afternoon with a lap of 190.215 mph.

Along with the teams collecting data, NASCAR continues to gather feedback and keep an open dialog with all the teams as the new season and competitive roll-out of the car approaches.

“All in all the feedback in the garage area has been very positive,” said Robin Pemberton, NASCAR vice president of competition. “It looks to me that all the hard work from the teams, manufacturers and our engineers at the R&D Center is going to pay off. Like I said last month when we hand this car off to the teams, it will be in the best shape that we have ever handed a car off to the teams to start a new season.”

In addition to test sessions at Daytona International Speedway and Charlotte next month, NASCAR will open for an extra day of testing at the 1.5-tracks of Las Vegas Motor Speedway and Texas Motor Speedway. Extra practice time is also slated for the event weekend at the 2-mile Auto Club Speedway in March.

Testing will conclude tomorrow.