Homogeneous charged compression ignition engines have significant advantages such as high thermal efficiency and low nitrogen oxide and particulate matter emissions simultaneously. The interest in alternative fuels is increasing globally to reduce dependence on fossil fuels. Fusel oil is obtained as a by-product in the production of ethyl alcohol. In HCCI engines, it is possible to control the combustion process with high octane fuels. Up to the present, no research has been conducted on the effects of fusel oil, which have high octane number, on combustion in HCCI engines. In this study, the effects of fusel oil on combustion, performance and exhaust emissions of HCCI engine at different lambda and inlet temperatures were investigated experimentally. The operation maps were obtained and parameters such as in-cylinder pressure, heat release rate, pressure rise rate, start of combustion, combustion duration, CA50, ITE and exhaust emissions were examined comparatively. The highest in-cylinder pressure was obtained as 71.96 Bar in the use of heptane fuel when lambda was 2.0 and engine speed 800 rpm. Maximum ITE was 45.4% with F60 fuel and lambda of 1.8. Under the same conditions, the ITE of heptane, F20 and F40 fuels were 29.1%, 32.7% and 34.7% respectively. At 353 K inlet temperature the highest CO emission was found to be 0.413% at 2.5 lambda when using F60 fuel. The highest HC emission at 353 K inlet temperature was 782 ppm when the lambda was 2.5 by using F60 fuel.