Methanol and diesel are not very miscible, which makes it difficult to mix them together as a diesel engine fuel. Dual-fuel operation is favored, and there is potential to reduce particulate matter (PM) and NOx emissions simultaneously. In this work, an electronically controlled low-pressure common rail system was employed to deliver methanol to the inlet port, while the engine's original high-pressure diesel injection system was used to deliver a suitable quantity of diesel fuel for ignition. The experimental results show that the full-load power of the dual-fuel engine can reach or even exceed that of the original diesel engine when a suitable minimum pilot diesel quantity is used. Under dual-fuel conditions, smoke is reduced significantly, while a modest reduction in NOx is observed. The equivalent brake-specific fuel consumption is improved under high-load operating conditions. Especially, the dual-fuel engine shows a better fuel economy when run at a high rate of methanol addition. However, unburned hydrocarbon (HC) and carbon monoxide (CO) emissions for dual-fuel operation increase when methanol is added.