Pfc. Quentin C. Johnson, front, and Lance Cpl. Joseph

Pfc. Quentin C. Johnson, front, and Lance Cpl. Joseph Lee, automotive organizational mechanics with 2nd Transportation Support Battalion, Combat Logistics Regiment 2, remove an exhaust pipe from the underside of an M1123 Humvee aboard Marine Corps Base Camp Lejeune, North Carolina, March 19, 2015. There are four levels of maintenance according to Johnson. The first is the basics, such as checking the oil, and the second is for corrective work, such as finding a basic part and ordering a new one should it require being replaced. The third is for engine repair, and the last tier is where the engine would be taken apart, fixed and put back together. (U.S. Marine Corps photo by Pfc. David N. Hersey/Released)