Operating load, rotational speed, and operating temperature must be considered when selected the proper grade oil to use. To measure viscosity, the Saybolt Universal Viscometer measures the time for 60 cubic centimeters of oil to flow through an orifice at a specified temperature. Relatively low viscosity oils are used in reciprocating engines. In a reciprocating engine, most heat is generated in the pistons and cylinders. An oil film forming a seal between the piston and connecting rod helps prevent chamber gases from leaking. Synthetic based oils deposit more lacquers and coke than petroleum based oils