This British Standard¹⁾ specifies a method for the determination of the manganese content of automotive gasoline, when the manganese is present as methylcyclopentadienyl manganese tricarbonyl (MMT®)²⁾. The precision of this test method only applies to the determination of manganese in the range of 10 mg/L to 40 mg/L, but higher concentrations can be measured by prior dilution of the gasoline sample with the specified solvent to bring the test portion within the specified range of the method. The test method may not be applicable to gasoline containing highly cracked components (less than 18% (V/V) olefins as determined by ASTM D1319 non depentanized). Solutions of MMT® in gasoline are chemically unstable when exposed to light, and low and erratic results are expected if the gasoline is exposed to light prior to stabilization during analysis.