The internal combustion engine (ICE) is a type of heat engine that converts chemical energy into mechanical energy. It finds application in various powered systems, including aircraft, jet engines, turbo engines, helicopters and many other machines. An ICE operates by igniting a fuel-air mixture, causing a rapid expansion of gases which drives piston or turbine that leads to turning the engine's crankshaft and generating power. This book is compiled in such a manner that it will provide in-depth knowledge about the theory and practice of internal combustion engine. In this book, constant effort has been made to make the understanding of the difficult concepts of internal combustion engine as easy and informative as possible, for the readers. The topics included herein are of utmost significance and bound to provide incredible insights to readers.