Kasey Kahne will no longer race in the NASCAR Cup Series full time after the 2018 season, he announced Thursday morning.

The 38-year-old Kahne, 28th in the series standings in his first year at Leavine Family Racing, has 18 career wins in 527 starts over a 15-year-career.

"I've thought about this decision for many months, if not longer," Kahne tweeted Thursday. "It's time for me to step away from racing in NASCAR full time. ... Racing in Cup full time for a few more years was just something that I couldn't commit to.

"I'm not sure what the future holds for me, but I know I'm at ease with the decision that I have made. The highs didn't outweigh the lows, and the grueling schedule takes a toll on your quality of life."

Debuting in Cup as a driver for team owner Ray Evernham in 2004, Kahne was with that organization as it was later bought by George Gillett and then merged with Richard Petty Motorsports. Late in the 2010 season, Kahne moved over to Red Bull Racing, which had hired him knowing he would leave after the 2011 season to drive for Hendrick Motorsports.

Hendrick released Kahne after last season, and he moved to the single-car Leavine operation.

Kasey Kahne says 2018 will be his final season as a full-time NASCAR Cup Series driver. Sean Gardner/Getty Images

Kahne won six races in just his third season in 2006 and finished eighth in points. His best points finish was fourth in 2012. He has won two races with 13 top-5s in the past five years. He also has eight Xfinity Series wins and five truck victories in six career starts in the series.

He owns teams that compete in the World of Outlaws sprint-car series. Kasey Kahne Racing driver Brad Sweet won the prestigious Knoxville (Iowa) Nationals on Saturday night.

"I need to spend more time doing the things I enjoy and love and that's spending time with [my 2-year-old son] Tanner and my sprint car teams," Kahne wrote. "I've had a great career in racing and met so many amazing people and fans along the way."

Kahne said on Friday that he would be willing to race in NASCAR occasionally if someone wanted a driver for races such as the Daytona 500, Brickyard 400 or another race but that he might never race in Cup again after Homestead. He also said he plans to run about 50 sprint-car races next year but looks forward to a life not consumed by racing.

"My mind is always in racing and it's all I've thought about for 25 years -- it's all I wanted to do and figure out how to get better as a driver, a team, understanding the cars," Kahne said. "It's always been on my mind. So to back off of it a little bit will be really refreshing and really good for me, my family and my friends."

Kyle Larson, who also owns sprint-car teams and competes against Kahne in those cars, said Kahne didn't give any indication of his decision during their flight last week to the Knoxville Nationals.

"I was surprised," Larson said. "I had no idea that he was going to be calling it quits. When we flew to Knoxville on Saturday, we somewhat talked about his situation and what he might do if he stays with his team or go to a different team.

"He didn't really say much. But I'm just really excited for him. All racing makes him happy -- NASCAR, sprint cars -- and spending time with Tanner he is going to really enjoy. ... He enjoys the hard work it takes to go fast in the sprint car. He is really into the setup stuff and trying to innovate and make his car better."

Well-wishes to Kahne came from throughout the NASCAR industry.

I'm so excited for you Kasey. You are a great friend. This is a hard decision. Much respect. https://t.co/9CkQAXsZ5d — Dale Earnhardt Jr. (@DaleJr) August 16, 2018

Leavine Family Racing now must find a driver for the 2019 season. The team already has informed Richard Childress Racing that it would end its alliance after 2018, and team owner Bob Leavine said Aug. 5 that the team was talking to other manufacturers.

If the team moves to Toyota, there has been speculation that Leavine Family Racing could hire Christopher Bell, a Toyota development driver currently running a Joe Gibbs Racing car atop the NASCAR Xfinity Series standings. Leavine said Aug. 5 that he had not talked to Bell.

"That was all news to me," Bell said Thursday at Bristol Motor Speedway when asked about Kahne's decision. "Right now I've got a great group of people and getting to drive for all of our partners. ... The only thing I've got is that I'm finishing out this year and then next year I'm going for the Xfinity championship again with all of our same partners."