Sunday Mark Martin won the Subway Fresh Fit 500 at Phoenix International Raceway. It was Martin’s first win in 97 races. His last win was at Kansas in 1995. He dominated the race, starting on pole and leading 157 of the 312 laps. In most forms of racing age 40 is the age where retirement is a requirement and not an option. But for Mark Martin at age 50, racing is a requirement. His workout regimen makes most twenty-somethings cringe. In Forumla 1 most retire or are released from their teams while still in their 30′s. But Mark Martin is thinking of the championship and not retirement.
A comprehensive study of every race winner & championship since 1949 shows that drivers who are a relative age of 31 (based on their age as of July 1 of that racing season) win more races and championships, on average. Of 2,174 total races recorded, drivers with a relative age of 31 have won 201 times, or more than 9 percent of the time. So age does seem to factor in. Since Dale Jarrett earned his title in 1999 at the relative age of 42, no driver over age 36 has won a championship. But then you have Harry Gant who did not win his first race until he was 42.
Mark Martin is not the oldest driver to win in NASCAR. Harry Gant is the oldest driver to win a Next Cup (formerly Winston Cup) race.
For a comparison:

Harry Gant, 52 years, 219 days at Michigan International Speedway on August 16, 1992
Morgan Shepherd, 51 years, 51 years, 147 days at Atlanta Motor Speedway on March 20, 1993
Mark Martin, 50 years, 99 days at Phoenix International Speedway on April 19, 2009
Bobby Allison, 50 years, 73 days at Daytona International Speedway on February 14, 1988

Mark Martin always one for protecting equipment even after a race prerserved the car. “No burnouts for me,” he radioed his crew. “Just a backward Polish victory lap for my man Alan Kulwicki.”