At the beginning of the work on the effects of global warming and climate change in the international area, there are efforts to reduce exhaust emissions. Because fossil fuel is depleting and exhaust emission gases emitted to the atmosphere are rising rapidly, energy efficiency is on the agenda in transportation. Therefore, automotive developers and scientists have undertaken new research in the automotive sector. Hybrid electric vehicle technology is one of the important studies that these researchers continue. In the hybrid electric vehicle technology, the hybrid engine is aimed to give the best results in terms of exhaust emission, fuel consumption and maintenance costs compared to other internal combustion engines, and at the same time the hybrid engine is aimed to perform better than other internal combustion engines. General information about the hybrid electric vehicle technology as one of the new and alternative technologies in these study is provided. In addition, information was given about exhaust emission, emission standards and fuel consumption. Comparisons were made between the hybrid engine and other internal combustion engines.