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They are currently used in many engine oils and, more recently, in gear oils. [1] They reduce friction by forming two-dimensional molybdenum disulphide layers on rubbing surfaces. [4] Functionalized polymers, which can be tailored to adsorb specifically on polar surfaces, have been shown to markedly reduce friction and wear. [5]
The 'bathtub curve' hazard function (blue, upper solid line) is a combination of a decreasing hazard of early failure (red dotted line) and an increasing hazard of wear-out failure (yellow dotted line), plus some constant hazard of random failure (green, lower solid line). The bathtub curve is a particular shape of a failure rate graph.
This significantly reduces engine performance, since the circular piston rings are unable to properly seal against the oval-shaped cylinder walls. The amount of sideways force is proportional to the angle of the connecting rod, therefore longer connecting rods will reduce the amount of sideways force and engine wear.
The power produced by an engine increases with the engine's RPM to a maximum, then falls away. The point of maximum power is somewhat lower than the absolute maximum engine speed to which it is limited, the "redline". A car's speed is limited by the power required to drive it against air resistance, which increases with speed.
Insufficient lubrication subjects the parts of the engine to metal-to-metal contact, friction, heat build-up, rapid wear often culminating in parts becoming friction welded together e.g. pistons in their cylinders. Big end bearings seizing up will sometimes lead to a connecting rod breaking and poking out through the crankcase.
Engine braking is a generally accepted practice and can help save wear on friction brakes. It is even used in some motor sports to reduce the risk of the friction brakes overheating. Additionally, fuel injection engines generally do not use fuel while engine braking. This is known as deceleration fuel cut-off (DFCO).
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Because modern diesel engines often have a throttle, EGR can reduce the need for throttling, thereby eliminating this type of loss in the same way that it does for spark-ignited engines. In a naturally aspirated (i.e. nonturbocharged) engine, such a reduction in throttling also reduces the problem of engine oil being sucked past the piston ...