A study on the temporary viscosity loss under high shear rates of engine lubricants was started in order to:
1.
Set up a new viscometer, more correlate with the engine than the present ones.
2.
Clarify the influence of this phenomenon on the lubricant performances.
Preliminary results on a pressoviscometer are discussed.
Namely it is underlined that the temporary viscosity loss affects both multigrade and unigrade oils, even if at different levels, and in different ways.
