Patent ID: 8026105

Claim:
A test method for testing engine lubricating oils and their additives using a constant volume combustion test device, comprising: selecting a sample of a lubricant composition to be tested; mixing the lubricant composition with a solvent to reduce the viscosity of the lubricant composition, thereby forming a sample having a predetermined ratio of the lubricant composition to solvent; wherein the lubricant composition is a substance under test and the solvent is introduced solely for the purpose of the test method; subjecting the sample to a constant volume combustion test to determine the ignition delay associated with the sample; associating the ignition delay with a reactivity index; repeating the above steps for an iterative range of samples, each sample having a predetermined lubricant-solvent ratios, thereby acquiring an iterative data set of measurement values from the constant volume combustion device, each measurement value having an associated lubricant-solvent ratio; applying statistical methods to the data set to calculate the reactivity of the lubricant composition without the solvent, without direct measurement of the lubricant composition without the solvent.