Idle Speed

The total rotations per minute (RPM) of an engine while it is free from any type of work or additional function. This measurement is more accurately taken when the engine is in the park or neutral position with all accessories and additional functions turned off and at a normal operational temperature.

Idler Pulley

A pulley equipped on a vehicle’s belt or a chain which is used to either guide those mechanisms or to tighten them to optimal tension levels.

Ignition Timing

A process used to set the specific time to fire a spark within an engine’s combustion chamber during its power stroke. This timing must remain relative both to the crankshaft angular velocity as well as the piston position for ideal operation. Proper ignition timing helps to stabilize vehicle startup and maintain its reliability for continued usage.


Shorthand for “Inherently Low-Emission Vehicle.” A vehicle emissions standard used in vehicles equipped with alternative-fuel engines. Closed and pressurized fuel systems can implement a lower level of emissions with these alternative fuels. The standard helps to distinguish vehicles which are designed to produce fewer emissions for an improved environmental impact.

Inboard Brakes

A vehicular braking system which is equipped in its chassis rather than it hubs. This braking position helps to reduce the total unsprung weight of wheel hubs, and they were primarily used in several older models of cars such as the 1960s Jaguar E-Type.

In-Car Cellular Phone

Cellular phone installation within a vehicle. Two primary options for this type of feature are available. First, a handset may be directly built into the vehicle’s dash or console. Second, a portable unit with an included dock is built into the system. Both options allow a mobile device to be used and heard through a vehicle’s entertainment and speaker system. It is frequently included as an added feature, and it can provide safer operation of a vehicle with integrated, hands-free usage.


An expansive variety of financial offers, discounts, and other incentives from a vehicle manufacturer to entice consumers to buy or lease a vehicle. This financial assistance may include a reduction in the current net price, reduction in the rate terms for finance agreements, cash rebates, lower interest rates for financing, and unsubsidized leasing agreements provided by the manufacturer. These incentives can be implemented to move inventory during slower sales periods or reinvigorate the sales of specific vehicle makes or models. In many cases, it can mark the deciding factor for a prospective buyer to purchase or lease.

Incentives and Rebates

An all-encompassing automotive industry term which includes every method and strategy manufacturers use to help stimulate or reinvigorate vehicle sales or leasing agreements. The primary goal of these incentives is to provide a marked reduction in the net cost to consumers through no reduction in the vehicle’s MSRP. This means that the MSRP remains the same, but additional factors can reduce the final price a prospective buyer or lessee will inevitably pay for the vehicle. These factors may include specific customer rebates, cash incentives provided to dealers for vehicle sales, and other special leasing terms which may reduce interest rates or reduce other related costs.

Individual Monitors

Each screen which is equipped in the rear passenger section of a vehicle’s cab included with rear-equipped video entertainment systems. Certain vehicle models may feature multiple monitors, most commonly behind the front driver and passenger seats.


Displays which provide all the vehicle driver information during operation. Depending on the vehicle, readouts can be provided in either digital or analog format (or a combination). They may include engine parameters and dynamic readouts of components, current operating conditions, the active engine RPMs, coolant temperature in the engine, and vehicle speed.

Instrumented Testing

Vehicle performance analysis used to verify optimal vehicle operation, identify problem areas, and indicate potential service concerns during operation. Precise equipment is utilized at specialist locations such as a dealership or mechanic’s garage to yield important data for diagnosis and repairs of various automotive issues.

Insurance Institute for Highway Safety

Abbreviated as “IIHS,” an organization involved with working toward the reduction of vehicle-related losses. This industry was created by the insurance industry as an additional tool to improve overall automotive safety while limiting financial losses. These losses include human injury or death as well as property damage to vehicles from accidents and crashes.

Integrated Turn Signal

Sideview-mirror mounted turning signal equipped to provide an additional external indicator when the driver initiates a turning process. This added indicator may improve vehicle safety with another visible sign of turns for other drivers.

Intelligent Alternator

An alternator which can be intelligently switched between passive and active usage depending on the current driving needs. When a vehicle does not require power in situations such as braking or coasting, the alternator detects current conditions and remains passive. During this time, a vehicle’s electrical requirements are powered by the battery. Once the conditions change, the alternator engages and continues active operation. This feature is used to improve fuel efficiency while driving. Working alongside other intelligent engine features, the system can also reduce a vehicle’s overall emissions and reduce its carbon footprint.

Intelligent Car

Vehicle which is equipped with all the latest technological advances in data reporting, automation, and efficiency. Intelligent features include driver and pedestrian alert systems, front, rear or side cameras, data-reporting telemetrics, and sensor-based brake engagement with collision detection.

Interior Lighting

Lighting sources which are equipped within the cab of a vehicle to improve visibility. Lighting is usually comprised of halogen lamps or LEDs, and it is automatically engaged when entering or exiting a vehicle. Lights can also be turned on or off by vehicle occupants at their discretion.

Interior Trim

The type of trim which is equipped throughout the interior cab of a vehicle. This provides a range of aesthetic appearances for vehicles with many makes and models offering multiple different options. Typical interior trims include leather, metal, wood, and composite.

Intermittent Wipers

Wiper setting which allows automatic engagement of the wipers with adjustable pauses between one windshield pass. Drivers can adjust the intermittent speed of the wipers based on current weather conditions.


Also known as the longhand “Invoice Price,” this is the amount which appears on a vehicle which is sent to a dealer from the manufacturer. Factory invoice prices are often standardized, but this price may also vary based on current cash incentives, regional price differentiation, time of the year when vehicles are shipped, and multiple other factors.