We have found chromogenic indicator reactions to test for anti-knock additives to gasolines: ferrocene, cymantrene, and N-methylaniline. Based on these reactions, we have developed methods for fast determination of the indicated additives in automotive gasolines using indicator tubes. The range of analyte contents are: 10-200 mg/dm(3) ferrocene, 10-150 mg/dm(3) cymantrene, 0.1-1.5 wt.% N-methylaniline.