Determine S.S.U. at Different Temps.

Which equation? Draw a straight line between the two points and you will not be terribly far out, but much better, just get the oil data sheet from the oil company (web site should do) with the curve already drawn for you.

Looks like homework to me. The LOP didn't even bother to alter the question, just copied it from the book/test.

Viscosity is NOT a linear function of temperature!

Usually, when the common log of viscosity is plotted against the inverse of Kelvin temperature it will form a double curved line (similar to the pH curve from titrating a strong acid with a strong base). There is a range of moderate temperatures where the logs of viscosity will be essentially linear and inversely proportional to the temperature (K). Although some variables (such as molecular weight) may be good predictors, empirical values of viscosity usually need to be determined for each substance (some are listed in handbooks).

http://www.ddbst.com/en/online/Online_Calc_visc_Form.php

what is the grade of oil ie 20/50 10/40 etc