Reproducibility of Oil Stability Index (OSI) values determined on the Metrohm Rancimat was measured with a single run and between experimental runs. Within a single experiment, a range of 0.13 h and a standard deviation of 0.066 h were determined. For multiple experiments, standard deviations of 0.24 and 0.26 were obtained for soybean and low‐erucic rapeseed oil, respectively. The effect of temperature was determined for safflower, soybean, lowerucic rapeseed, corn, peanut and olive oils. A linear relationship was established between log (OSI) and temperature. The linear equation obtained for soybean oil was utilized to calculate variability of the OSI due to temperature differences in the heating block.