In this paper higher fatty acids composition, peroxide and acidic value and density of raw commercial rape oil and of oil fraction formed after each of five cycles of oil heating conducted in two ways - with and without potato chips frying, were compared. After each heating, which duration corresponded to time necessary for potato chips frying, oil was left to cool down (to room temperature) and stored in conditions similar to ones found in small gastronomy. Goal of undertaken research was usability assessment of used frying rape oil as a substrate for biofuel production. Utilization of used frying rape oil as fuel seems to be grounded by favourable ratio of saturated and unsaturated fatty acids in oil fraction, which properties stabilize as a result of surface contact with potato chips, as well as by ecological (utilization of waste), energetic (replacement of conventional crude oil based fuels) and economical (utilization of cheap wastes) reasons.