Based on the physical properties, Chemical fuels are classified as solid, liquid and gaseous. The use of a particular type of fuel depends on the type of application and the design of a combustion device. Chemical fuels pass through a number of stages namely extraction, purification and then go to their end-use. Nevertheless, the testing of fuel at each stage is necessary in order to ensure that the fuel meets International Standards. This book aims to provide different fuel testing methods along with their detailed theoretical concepts. This book is written for undergraduate engineering students in junior or senior years, studying fuel and energy engineering. The intended readers of this book also include students enrolled in fuel engineering diplomas and trainee fuel-laboratory technicians. The contents of this book cover the basic and advanced concepts, necessary to understand fuel testing. Therefore, no prior knowledge about fuels is required to read this book. It includes properties and testing of all three types of Chemical fuels.