ELLSWORTH AIR FORCE BASE, S.D. -- Airman 1st Class Joshua Dunn, 28th Logistics Readiness Squadron vehicle maintainer, checks the dip-stick from his engine to see if the engine needs oil, July 28. It's important to check the oil in an engine every 3000 miles and have it replaced to keep the engine in peak performance. (U.S. Air Force photo/Airman 1st Class Anthony Sanchelli)