Use of bio-oils in diesel engines results in increased NOx and smoke and reduced brake thermal efficiency. Dual-fuel engines can use a wide range of fuels mainly alcohols and yet operate with high thermal efficiency and simultaneous reduction of NO and smoke emissions. The present study aims to explore the effect of methanol-waste cooking oil (WCO) dual-fuel mode on performance and emission characteristics in a single cylinder Compression ignition (CI) engine producing 3.7 kW at 1,500 rpm. WCO was injected in the conventional injection system, replacing diesel as pilot fuel. Methanol was fumigated along with intake air using a variable jet carburetor, which was installed in the inlet manifold. The methanol was fumigated, and the energy share was varied for each load till the knock limit. Performance parameters like brake thermal efficiency (BTE) and emission parameters like HC, CO, NO, and smoke emissions were tested for various energy shares of methanol with WCO as a pilot fuel. The results show that an increase in methanol fumigation reduced BTE at lower loads. At 75% and 100% load conditions, BTE was higher with methanol addition. The maximum BTE was observed for 38% methanol share, which is about 11% higher, compared to WCO at 100% load condition. Methanol fumigation aided in the simultaneous reduction of NO and smoke emission, and the maximum reduction was occurred with 51% methanol share at 100% load condition. HC and CO emissions were higher at all load conditions with methanol fumigation.