The Redwood Viscometer No. 1 is the classical British standard instrument for measuring the efflux viscosity of lubricating oils. In this experiment, oil is heated to a controlled temperature in the viscometer's oil cup, and the time (in Redwood seconds) for exactly 50 mL to drain through the calibrated 1.62 mm orifice jet is measured at both room temperature and 60°C. The empirical Redwood formula, nu = 0.26t − 179/t (cSt), converts efflux time to kinematic viscosity in centistokes; results are compared against SAE viscosity grade specifications. The chapter provides a detailed treatment of the viscosity index (VI) — a measure of how much viscosity changes with temperature — and explains why a high VI is essential for multi-grade lubricants used in variable-temperature environments. The relationship between Redwood, Ostwald, and Saybolt viscometers is explained, and conversion factors are provided. The percentage decrease in viscosity on heating from room temperature to 60°C is calculated and interpreted in the context of oil film strength and lubrication failure.