In this study, dynamic viscosities of fuels of raw hazelnut oil and raw hazelnut oil methyl ester are measured in the interval of 0-100 degrees C with 10 degrees C intervals using a Brookfield Engineering Co., USA DV-II+ Pro rotary viscosity-meter The experiments are conducted under 20 degrees C ambient temperature. Viscosity measurements are performed at 50 rpm constant speed by using a RVII spindle. Data are recorded in 5 sec intervals using Brookfield Engineering Co., Win gather software. Dynamic viscosities of fuels of raw hazelnut and raw hazelnut methyl ester have obtained a decrease by increasing temperature and diesel concentration. Using the dynamic viscosities of raw hazelnut oil methyl ester and diesel fuel, dynamic viscosities of B50, B20, and B5 fuels with respect to temperature are estimated by using Arrhenius mixture equation. In addition to this, using a modified Andrade equation, regression analyses are conducted in MATLAB (R) software and R-2, absolute error and error percentages are determined in the interval of 0-100 degrees C with 10 degrees C intervals.