A green vehicle, clean vehicle, eco-friendly vehicle or environmentally friendly vehicle is a road motor vehicle that produces less harmful impacts to the environment than comparable conventional internal combustion engine vehicles running on gasoline or diesel, or one that uses certain alternative fuels. Presently, in some countries the term is used for any vehicle complying or surpassing the more stringent European emission standards (such as Euro6), or California's zero-emissions vehicle standards (such as ZEV, ULEV, SULEV, PZEV), or the low-carbon fuel standards enacted in several countries. Green vehicles can be powered by alternative fuels and advanced vehicle technologies and include hybrid electric vehicles, plug-in hybrid electric vehicles, battery electric vehicles, compressed-air vehicles, hydrogen and fuel-cell vehicles, neat ethanol vehicles, flexible-fuel vehicles, natural gas vehicles, clean diesel vehicles, and some sources also include vehicles using blends of biodiesel and ethanol fuel or gasohol. In 2021, with an EPA-rated fuel economy of 142 miles per gallon gasoline equivalent (mpg-e) (), the 2021 Tesla Model 3 Standard Range Plus RWD became the most efficient EPA-certified vehicle considering all fuels and all years, surpassing the 2020 Tesla Model 3 Standard Range Plus and 2019 Hyundai Ioniq Electric. Several authors also include conventional motor vehicles with high fuel economy, as they consider that increasing fuel economy is the most cost-effective way to improve energy efficiency and reduce carbon emissions in the transport sector in the short run. As part of their contribution to sustainable transport, these vehicles reduce air pollution and greenhouse gas emissions, and contribute to energy independence by reducing oil imports. An environmental analysis extends beyond just the operating efficiency and emissions. A life-cycle assessment involves production and post-use considerations. A cradle-to-cradle design is more important than a focus on a single factor such as energy efficiency. Energy efficiency Cars with similar production of energy costs can obtain, during the life of the car (operational phase), large reductions in energy costs through several measures: The most significant is by using alternative propulsion: An efficient engine that reduces the vehicle's consumption of petroleum (i.e. petroleum electric hybrid vehicle), or that uses renewable energy sources throughout its working life. Using biofuels instead of petroleum fuels. Proper maintenance of a vehicle such as engine tune-ups, oil changes, and maintaining proper tire pressure can also help. Removing unnecessary items from a vehicle reduces weight and improves fuel economy as well. Types Green vehicles include vehicles types that