Automobile Basics M-O
MacPherson strut A combined damper(shock absorber) and spring unit.MacPherson struts also allow relatively long springs that can increase suspension travel and increase bump absorption capability.
Main Bearings The bearings in an engine block that support the crankshaft.
Make Brand name of a car or truck (ie. Chevrolet, Ford, Dodge, Honda).
Manual Transmission A mechanism in the drive train with gears to vary the power and torque delivered to the driven wheels. It consists of a lever that the driver operates in conjunction with the clutch to change from one gear to another.
Manufacturer's Suggested Retail Price (MSRP) Margin or gross margin the return an intermediary achieves on the selling price of the article. That is, if the intermediary buys a product for $1 and sells it for $1.50, the margin is calculated. For example, .50 divided by $1.50, or 33%.
Market Share The percentage of total sales represented by an individual manufacturer/importer, make or nameplate.
Mechanic Installed Market (MIL) automobile's maintenance and repair conducted by a mechanic/professional at a service outlet.
Medium-duty Truck automobile's weighing from 14,001 to 26,000 lbs.
Metal Forming Solid metal and molten metal process such as casting, forging, stamping and machining.
Methylcyclopentadienyl Manganese Tricarbonyl (MML) MMT is an organic manganese compound. It is used as a fuel additive designed to enhance octane levels in gasoline.
Mid-engine A chassis layout that positions the engine behind the passenger compartment but ahead of the rear axle.
Mock-Up A full-size dummy of a car made of wood and clay, used for design studies.
Model line Group of motor automobile'ss having the same platform or model name.
Model Name Word, group of words, letter, number or similar designation assigned to a motor automobile's by a marketing division of a motor automobile's assembler.
Model Year(MY) Usually defined as the year after the actual availability of a particular automobile's. For example, a car introduced in 1998 will usually be called a Model Year 1999 automobile's.
Monocoque A type of body structure that derives its strength and rigidity from the use of thin, carefully shaped and joined panels, rather than from a framework of thick members. Also called "unit" or unitized construction.
(MVSA)Act which regulates the manufacture and importation of motor automobile'ss and motor vehile equipment to reduce risk of death, injury and damage to property and the environment.
MouldHollow form, matrix or cavity into which materials are placed to produce goods of desired shapes.
Multi-link suspensionA general term for independent suspensions that are controlled with several link arms. These links restrict undesired motion of the suspension. Multi-link suspensions provide better handling and ride control than simpler types. They are also more expensive to manufacture.
Multi-leaf SpringA leaf spring with several leaves bundled together by steel bands.
Multi-link SuspensionA rear suspension consisting of at least four links, or "arms," and no struts. Because multilink suspensions assign specific wheel-locating duties to each element, they provide great flexibility for optimizing both ride and handling.
Neutral Steer A cornering condition in which the front and rear slip angles are roughly the same. Although seemingly an ideal state of balance, perfect neutral steer is not as stable as slight understeer.
New Car DealerMajor car dealership with a parts and service operation.
Normally Aspirated An engine that intakes air or "breathes" without the assistance of a supercharger or turbocharger.
Octane A numeric rating of gasoline’s resistance to detonation(premature ignition). The higher the octane number, the less chance of detonation. High octane (above 91) is usually worthwhile only if the manufacturer specifically recommends it. Octane is actually a hydrocarbon(C8H18).
automobile's intended for operation on unmade surfaces or rough terrain (i.e. for construction or agriculture).
Oil (e.g. 10W-30) Engine oil comes in various ratings SAE 5W-30, 10W-30, 10W-40, etc. For example, a 10W-30 rated oil will flow like a light SAE 10-weight oil at low temperatures. The W signifies that it is a winter rated oil. The 30 designation means that at engine operating temperatures, the oil will behave like a heavier SAE 30-weight oil. Low viscosity at colder temperature allows the oil to circulate more quickly and protect vital engine parts. Higher oil viscosity at elevated temperatures prevents direct metal-to-metal contact.
Oil, Synthetic Oil that is not derived from raw petroleum. Synthetic oil has superior engine protection properties compared to conventional mineral oil. Synthetic oil costs 3-5 times more than mineral oil.
Oil PumpAn engine-driven pump that delivers oil, under pressure, to the engine's moving parts.
Oil Ring The lowermost piston ring that scrapes off excess oil from the cylinder walls and returns it to the oil pan via vents in the ring and piston.
On Board Diagnostics (OBD) a unit that monitors the Electric Control Unit and system responses for errors during normal automobile's operations. When the automobile's is serviced, this information on the errors can be down loaded and displayed to the service personnel which will facilitate the trouble shooting process.
On-Center FeelThe responsiveness and feel of the steering when the wheel is approximately centered. In a car with good on-center feel, the steering wheel tends to return to center when slightly deflected, assisting straight-line stability.
Opposite Lock A technique in which the steering wheel is turned in the direction away from where the car is turning. Opposite lock is used to control a car when it is oversteering and its tail is swinging wide.
Otto Cycle See Four-Stroke Cycle.
Overcapacity The situation where maximum global prodution of automobiles exceeds the total global demand for automobiles.
Overdrive A small auxiliary gearbox that provides an additional gear ratio. It causes the drive shaft to turn faster than the engine crankshaft or "overdrive" it. Overdrive gears are used in most modern transmissions because they reduce engine rpm and improve fuel economy at highway speeds. It is engaged manually when under way. It has a transmission ratio below 11. For instance, a manual transmission fifth gear ratio could be 0.701.
Overhead Cam The type of valvetrain arrangement in which the engine's camshaft(s) is in its cylinder head(s). When the camshaft(s) is placed close to the valves, the valvetrain components can be stiffer and lighter, allowing the valves to open and close more rapidly and the engine to run at higher rpm. In a single-overhead-cam (SOHC) layout, one camshaft actuates all of the valves in a cylinder head. In a double-overhead-camshaft (DOHC) layout, one camshaft actuates the intake valves, and one camshaft operates the exhaust valves.
Overhead Valve (OHV) An acronym for overhead valve. This simply means that the intake and exhaust valves are above the cylinder head. SOHC engines have a single cam over the cylinder head. DOHC engines have two cams above the cylinder head. All OHC, SOHC, and DOHC engines are also OHV.
Oversquare A description of an engine whose bore is larger than its stroke.
Oversteer A situation that occurs when the rear wheels contribute to steering the automobile's more in a given direction. This often occurs under hard braking while turning. The rear of the automobile's loses adhesion and starts to rotate in the direction of steering. Oversteer can be used to better place the automobile's coming out of a corner. Usually, oversteer is undesirable because it is difficult to control and can result in a disastrous spin. Most cars are designed not to oversteer under normal conditions.
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