This test method provides a means of calculating the mean relative molecular mass of petroleum oils from another physical measurement.

Mean relative molecular mass is a fundamental physical constant that can be used in conjunction with other physical properties to characterize hydrocarbon mixtures.

1.1 This test method covers the estimation of the mean molecular weight (relative molecular mass) of petroleum oils from kinematic viscosity measurements at 100 and 210°F (37.78 and 98.89°C). It is applicable to samples with molecular weights in the range from 250 to 700 and is intended for use with average petroleum fractions. It should not be applied indiscriminately to oils that represent extremes of composition or possess an exceptionally narrow molecular weight (relative molecular mass) range.

1.2 Values stated in inch-pound units are to be regarded as the standard. The values given in parentheses are provided for information purposes only.

1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.