Formula One glossary

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Oblique crash test

The oblique crash test determines a vehicle\'s ability to withstand crashes which may occur to any of its four corners.

Octane number

Indicator of capacity for a product to resist high pressures without spontaneous combustion occurring also known as resistance to knocking. When the numbers were first developed, the researchers found that normal heptane (a hydrocarbon) had almost no ability to resist knocking so they gave it an octane number of zero. Then they found that isooctane (also a hydrocarbon) was very resistant to knocking so they gave it the octane number of 100. To measure a particular sample of gasoline they discovered when it began to create detonation. Then they mixed isooctane to heptane to find out what percentage of isooctane created the same results as the sample of gasoline. There are two methods for determining the octane number depending upon operating conditions. The Research Octane Number (RON) is obtained when conditions are somewhat mild. The Motor Octane Number (MON) is obtained when conditions are somewhat severe and give a much lower number than the RON.


A substance that lubricates and cools the moving parts of the engine and reduces the formation of rust and corrosion. It contains additives which fights the corrosion of bearings, keeps small particles in suspension, reduces engine wear, and reduces oxidization, minimizes carbon, lacquer, and gum formation. Oil comes in varying viscosity weights suitable for efficient operation in cold and hot weather and for engines in varying states of wear.

Open wheel

Refers to any type of racecar that does not have enclosed wheels. Formula One, CART, F3000 and Formula Atlantic are open-wheel cars.

Otto cycle

Thermodynamic cycle used in engines, in which combustion is fired by a spark. Its fuel is gasoline, alcohol or a mix of both. All cylinder engines powered by gasoline are based on this principle.

Overhead camshaft (OHC)

The camshaft that activates the valves is mounted above the head and driven by a long timing chain or cam chain. In contrast, a pushrod engine has the camshaft below the cylinders so that thin rods (pushrods) are moved by the camshaft and activate the valves. An engine with an overhead cam means that the distance between the cam and the valves is much shorter, so the valves respond quicker and valve adjustment can be more accurate. Also this system allows for higher engine speed because of fewer moving valvetrain parts. A system with only one cam is called "Single Overhead Cam" (SOHC). In some instances there are two camshafts above the heads (one for the intake valves and the other for the exhaust) and called "double overhead cam" (DOHC).

Overhead valve (OHV)

Valves located in the head. A four-stroke engine with the intake and exhaust poppet valves located in the cylinder head and not at the side of the cylinder as in a side-valve engine. The valve stems are either at an angle or parallel and the valve discs face the piston, valve actuation pushrod and swing arm.


In cornering, oversteer exists when the rear end of the car tends to make a larger radius turn than the front end. The rear end of the vehicle wants to swing toward the outside of a turn. It is generally a sign that the suspension roll resistance is too hard in the rear or too soft in the front. A rear-engine vehicle has a natural tendency to want to swap ends, or oversteer, unless its suspension is adjusted to counteract it. A handling condition in which the slip angles of the rear tires are greater than the slip angles of the front tires. An oversteering car is sometimes said to be "loose", because its tail tends to swing wide.