Oil Cups
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On some vehicles there are parts of the drivetrain that can only be lubricated manually.
They usually have small oil cups scattered around. Opening their caps will reveal the oil level inside of each. Each of the cups needs to be refilled using an oiler. Then the caps should be closed, to prevent oil from being spilled out.
See also: Lubrication, Oiler, Automatic Lubricator, Mechanical Powertrain Damage, Servicing