Motorboy,
I NEVER SPOKE OF KLOTZ BENOL. If it is castor oil is castor oil, at the very end the brand really makes little difference, and nature never made any two, three or four strokes oil, it made oils, that can fit or not whatever you would fit, and castor oil fits well engines and intestines, and many more.
A viscosity can be measured at every temperature and value, also glass has one, the difficult is to make it pass throug a hole, it takes a bit too much time. You can use cup viscometers also with molten metals! The only rule is to control drop formation. At that point viscometer does not measure since surface tension prevails on flow.
The reason of fixed temperature measurement is to mantain comparability between different batches under measurement. No other reason, since ordinary temperatures do not affect neither the size of the cup nor that of the hole. Fixed temperature measurements are customary since cup viscometers are mainly used as production control instruments due to the simplicity of operation, so also an inexperienced tester can quickly follow on the field the viscosity of what is in productio and take the opportune measures in real time, think of a paint production line.
You can use your cup viscometer until it melts, the real problem is to calibrate it, not to use standard calibration. This gives more accuracy, and I used calibrating solutions for it.

Ugo