1. I have all the data to calculate the power absorbed by a car engine using the Petrov equation at 100C. I know the oil viscosity at -20C which would allow me to calculate power absorbed at this temperature. The question is asking for the max speed it could run at in this cold start condition if the engine can deliver 60kW. 2. I have all the information on the Petrov equation but how is this rearranged to give the start up speed. 3. My thoughts are that I work out the power loss at this cold temperature and find it as a percentage against the hot running power loss and then use that percentage against the input power of 60kW. Or, I had thought of calculating the percentage difference in the kinematic oil viscosities at cold at hot temperatures then using this against the 60kW input power.