ELLSWORTH AIR FORCE BASE, S.D. -- Airman 1st Class Joshua Dunn, 28th Logistics Readiness Squadron vehicle maintainer, pulls the dip-stick out of his engine to check the oil, July 28. It's important to check all engine fluids periodically to ensure peak performance of the engine. (U.S. Air Force photo/Airman 1st Class Anthony Sanchelli)