The operating ranges of Micro-Ubbelohde viscometers of capillary numbers II, IIc and III were defined and the validity of working equations was verified with the aim to optimize the measuring times for measurements in the mineral oil industry and petrochemistry. In the submitted paper at first the results are presented as an example by means of modified static device characteristic curves of a Micro-Ubbelohde viscometer of capillary number IIc. The minimum flow times and the minimum measurable viscosities according to the experimental results are summarized in comparison with the measuring ranges following DIN 51562 Part 2. The application of Micro-Ubbelohde viscometers allows a decrease in measuring time of about a third of the minimum flow time of 30 s according to DIN 51562 Part 2 without a significant reduction in measuring accuracy. Further advantages are a shorter time for temperature adjustment and a smaller drift of the flow times.