Maintaining a fleet of heavy vehicles isn't easy, and even something as seemingly straightforward as motor oil selection can turn into a significant purchasing decision. When you're buying lubricants for an entire fleet, small choices can drastically alter your maintenance costs. Choosing the right oils is a small but necessary part of keeping your fleet running reliably and cost-effectively. Since most heavy equipment motors use diesel engines, your oil selection is, in part, dictated by EPA emissions standards.