Suburban Propane Partners, L.P. (NYSE:SPH) has become the Official Propane of NASCAR and Speedway Motorsports through a multi-year partnership. Speedway Motorsports owns 10 tracks that host NASCAR races, including Dover Motor Speedway. Suburban Propane is a Whippany, NJ-based nationwide distributor of propane, renewable propane, renewable natural gas, fuel oil, and related products and services, as…