Patent ID: 8557589

Claim:
A method for quantitative analysis of engine oil having an unknown concentration of dye, the method comprising: preparing a diluted test sample by diluting a test sample of the engine oil with a non-reactive solvent, and calculating the dilution factor by the formula: dilution factor of test sample equals Total Mass of diluted test sample (grams) divided by mass of original test sample (grams); preparing a stock solution by adding a known weight of dye to a known weight of new engine oil; preparing two or more standard solutions by adding incrementally-increasing weights of said stock solution to said diluted test sample; measuring absorbance values of said two or more standard solutions by spectrophotometry; measuring by spectrophotometry the absorbance values of the diluted test sample; determining the concentration of the dye in the test sample based upon the measured values of said two or more standard solutions and the concentrations of dye added; and comparing the concentration of dye in the test sample with a desired concentration of dye in the engine oil to quantify the amount of dye to be added to said engine oil to bring the dye concentration to the desired concentration.