We purchased an assortment of retail aftermarket gasoline additives from many manufacturers with the intention of evaluating the contents to compare the active ingredients available in the package with the product performance and benefit claims as advertised on the label. We did an initial screening to determine a gross actives level through a low temperature non-volatile matter determination. We then sorted the products into groups according to their type of claim. Further infrared spectrographic analysis determined chemical content and confirmed the initial quantitative work. This information let us determine whether the manufacturer's choice of active ingredients was appropriate to provide the particular benefits claimed and whether there was enough to do the job.