This standard is concerned with the method of determination of ash from distillate and residual fuels, crude oils, lubricating oils, waxes and other petroleum products in which any ash-forming materials present are normally considered to be undesirable impurities or contaminants (Note 1). The method is limited to petroleum products which are free from added ash-forming additives, including certain phosphorus compounds (Note 2). NOTE: 1 In certain types of samples, all of the ash-forming metals may not be retained quantitatively in the ash. This is particularly true for distillate oils, which require a special ash procedure in order to retain metals quantitatively. NOTE: 2 This method is not intended for the analysis of unused lubricating oils containing additives; for such samples use Gulf Standard GS 130 “Determination of Sulfated Ash from Lubricating Oils and Additives”, neither is it intended for the analysis of lubricating oils containing lead nor for used engine crank case oils.