A gun oil composition adapted specifically for the needs and requirements of modern firearms. The gun oil composition improves lubricity and gun performance under normal and extreme heat and pressure, minimizes and largely prevents the build-up of carbon and debris fouling on metal and non-metal components of the firearm, and substantially reduces cleaning time, while providing increased protection against environmental components such as dust, dirt and rust. The gun oil composition can include a base oil having at least a high viscosity index, an oil having at least a medium viscosity index with a detergent additive, a low viscosity penetrating oil, and a sulfurized ester.