Audi A8 4.0 AT Security Specs — Fourth Generation Restyling 1

The highest speed a vehicle can sustain under manufacturer test conditions. Some cars are electronically limited below their mechanical potential. Glossary entry

A turbocharger or supercharger compresses the air entering the engine so a smaller engine can produce more power. Naturally aspirated engines draw air without a compressor. Glossary entry

Which wheels receive power: front-wheel drive, rear-wheel drive or all-wheel drive. All-wheel drive can send power to every wheel for extra traction. Glossary entry

The diameter of a cylinder (bore) and the distance the piston travels inside it (stroke). Together they determine the displacement of the engine. Glossary entry

The total volume swept by all pistons inside the cylinders, usually stated in cubic centimetres or litres. Larger displacement often means more power but higher consumption. Glossary entry

How many fixed forward ratios a gearbox offers. More gears can improve economy and refinement; continuously variable transmissions have no fixed steps. Glossary entry

A unit of engine or motor output. One metric horsepower is about 0.735 kilowatts. Peak power is normally reached at high engine speed. Glossary entry

A unit of engine or motor output. One metric horsepower is about 0.735 kilowatts. Peak power is normally reached at high engine speed. Glossary entry

The ratio between the largest and smallest volume of a cylinder as the piston moves. Higher ratios improve efficiency but may require higher-octane fuel. Glossary entry

The time a vehicle needs to reach 100 km/h from a standstill, a common shorthand for overall performance. Glossary entry

The number of intake and exhaust valves in each cylinder. Four valves per cylinder is common and helps the engine breathe at higher speeds. Glossary entry

A car with a small electric motor and battery that assist the combustion engine and recover braking energy but cannot drive on electricity alone. Glossary entry

The amount of carbon dioxide released per kilometre under a standardised test. Lower figures usually go hand in hand with lower fuel consumption. Glossary entry

The distance an electric or plug-in vehicle can travel on a full charge under a stated test cycle. Temperature, speed and load change the real result. Glossary entry

The distance an electric or plug-in vehicle can travel on a full charge under a stated test cycle. Temperature, speed and load change the real result. Glossary entry

The distance between the centres of the front and rear wheels. A longer wheelbase usually gives more cabin space and a calmer ride; a shorter one helps agility and parking. Glossary entry

The distance between the centres of the two wheels on the same axle. A wider track generally improves stability in corners. Glossary entry

The distance between the centres of the two wheels on the same axle. A wider track generally improves stability in corners. Glossary entry

The weight of the vehicle with all standard equipment and fluids but without passengers or cargo. Glossary entry

The gap between the lowest point of the underbody and the road. More clearance helps on rough roads and steep driveway ramps. Glossary entry

The gap between the lowest point of the underbody and the road. More clearance helps on rough roads and steep driveway ramps. Glossary entry