One of the most important properties measured for liquid fuels is the volatility, usually expressed by the distillation curve. In previous work, we introduced the composition-explicit or advanced distillation curve (ADC) metrology, which we have applied to a wide variety of liquid fuels including biodiesel fuels. Application of this method to high-boiling-point fluids such as oils has required the addition of an inert-gas purge in the apparatus. Despite this precaution, there is clear evidence of thermal decomposition or polymerization at high distillation temperatures. To address this complication, a low-pressure version of the ADC was introduced. In this work, we have applied the low-pressure ADC method to the study of virgin and waste engine (motor) oils (5W-30, 10W-30, 20W-50), reclaimed comingled oil, reclaimed cutting oil, and used transformer oil. The results parallel similar measurements performed at atmospheric pressure, but with little evidence of chemical decomposition.