Viscosity of olive oil has been proved to increase with pressure, so it fits engine needs. Various types of olive (apart from the crop) differ mainly for the presence of free fatty acids. The more the free fatties, the less the quality and the more disturbing the extraction method. This is important for alimentary purposes, but probably does not mean anything for model engines, since they spit quickly the oil, without possibility of chemical modification. So the cheapest olive performs as the costlier ones. What is important is to "feel" the viscosity. This depends on the crops and on the brands.
Now I have the viscometer useful for high temperature-low viscosity measurements, wait for more data after calibration. But who introduced olive oil here?
Ugo