BOSTON (CBS) – There is no doubt in Jimmie Johnson’s mind which course is tougher when it comes to NASCAR versus Boston Marathon.

“Twenty-six without a doubt,” Johnson said when asked if it’s harder to run 200 miles in a race car or 26 on foot.

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Johnson crossed the finish line in 3 hours, 9 minutes. He was aiming to finish in under three hours, but was still thrilled with the accomplishment.

“It’s been an amazing experience. I’ve learned so much about myself. I just can’t believe how the city supports all the runners on the course,” Johnson told WBZ-TV.

NASCAR driver Jimmie Johnson crosses the Boston Marathon finish. line. (WBZ-TV)

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Johnson received his Boston Marathon bib through a sponsor’s exemption. He said the first half of the race “was so easy” but suddenly Johnson realized he had started too quickly.

“I wish I had my car at Heartbreak Hill,” Johnson joked. “It would have made it a lot easier.”

The driver added that he wanted to do his best to be “Boston Strong” after seeing coverage of the 2013 Boston Marathon bombings.

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“What an incredible experience,” he said.