A unit of measurement indicating the tendency of a fuel to detonate or knock based on the percentage of iso-octane in the fuel. The higher the rating of a fuel, the higher the percentage of iso-octane and the greater the resistance to detonation.
Odometer
A device used to measure and register mileage throughout a vehicle’s lifetime. Many vehicles also offer trip odometers that can be reset to measure distance traveled during any given trip or time period.
OHC (Overhead Cam) Design
See SOHC.
OHV (Overhead Valve) Design
An engine design in which the valves are in the cylinder head and the camshaft is within the engine block, and which requires pushrods and rocker arms to actuate, or open, the valves.
On-Board Diagnostics II System (OBD II)
The On-Board Diagnostics II System continuously monitors the powertrain and records any defects and wear of 50 different components. This allows Service Technicians to diagnose intermittent engine problems, to help reduce service time and cost.
On-center Feel
The responsiveness and feel of the steering when the steering wheel is approximately centered. In a vehicle with good on-center feel, the wheel tends to return to center when slightly deflected, providing good straight-line stability.
One-Touch-Down Driver’s Power Window
This feature provides the driver with a One-Touch-Down button that completely lowers the driver’s window for hands-free convenience. The window also can be lowered and stopped at any position. Refer to individual vehicle sections for availability.
Opposite Lock
A driving technique in which the steering wheel is turned in the direction away from where the vehicle is turning. Opposite lock is used to control a vehicle when it is oversteering and the tail is swinging wide as the rear tires begin to lose their grip.
Overdrive
A final transmission/transaxle gear ratio of less than 1:1 that is designed for economical highway driving. The overdrive gear allows the engine to operate at lower rpm while maintaining the given vehicle speed, thus requiring less fuel because the engine is doing less work.
Oversteer
A condition in which a vehicle turns more than the steering wheel input would dictate, generally caused by greater slip angles of the rear tires. It can make car control hard to maintain (the rear end tends to swing out). Engineers design suspensions to counteract oversteer by having understeer or neutral steering qualities.
