Marathon Oil Corporation NYSE: MRO, based in Houston, Texas, is a worldwide oil and natural gas exploration and production company.
It's NASCAR sponsorship began when it appeared on the #51 Competitive Edge Motorsports Chevy beginning at Chicagoland in 2004, taking the quarter panels. Eventually, Marathon and it's American Spirit Motor Oil became the primary sponsors on the car, until August 2006.
At that time, CEM announced they were shutting down and Marathon moved its sponorship to the #45 Petty Enterprises Dodge of Kyle Petty. Marathon will be the primary in a select number of races as well as an associate sponsorship for the rest of the year will both the #45 Petty car, but the other Petty Enterprises car, the #43.