Snowmobile engine emissions are of concern in environmentally sensitive areas, such as Yellowstone National Park (YNP). A program was undertaken to determine potential emission benefits of use of bio-based fuels and lubricants in snowmobile engines. Candidate fuels and lubricants were evaluated using a fan-cooled 488-cc Polaris engine, and a liquid-cooled 440-cc Arctco engine. Fuels tested include a reference gasoline, gasohol (10% ethanol), and an aliphatic gasoline. Lubricants evaluated include a bio-based lubricant, a fully synthetic lubricant, a high polyisobutylene (PIB) lubricant, as well as a conventional, mineral-based lubricant. Emissions and fuel consumption were measured using a five-mode test cycle that was developed from analysis of snowmobile field operating data. Emissions measured include total hydrocarbons (THC), carbon monoxide (CO), nitrogen oxides (NOx), carbon dioxide (CO2), particulate matter (PM), polycyclic aromatic hydrocarbons (PAH, both particulate bound and vapor-phase), and individual hydrocarbon species (C1-C12). Emissions and fuel consumption using bio-based fuels and lubricants were compared to results using a conventional fuel and lubricant. Promising candidates were identified and recommended for further study in a field demonstration in Yellowstone National Park.