Therefore, a very careful approach is suggested when choosing these instruments. It was also found that the results obtained with the use of the mid-FTIR spectrophotometer were burdened with a very large measurement error. Consistent outcomes were obtained for the Stabinger viscometer only, whereas the microchannel viscometer and the mid-FTIR spectrophotometer were not as precise as the reference method.
The main data analysis tools used in the study were multiple regression, Mahala Nobis distance, post-hoc analysis, and the Wilcoxon signed-rank test with the Bonferroni correction. The study material comprised 42 fresh engine oils, all of which are commercially available. The following instruments were selected to measure: a mid-FTIR spectrophotometer, a microchannel viscometer, and a Stabinger viscometer. The aim of this paper is to compare the results of kinematic viscosity of lubricating oils measurements at 40 ☌, obtained with three different rapid evaluation devices, and the standardized method using an Ubbelohde Capillary viscometer.
