US Patent 9587533 Oil level display device of engine

An oil level display device is fitted such that a float guide accommodating a float is attached to an oil filler neck and is plugged with a float cap. To check the amount of oil, the float cap is removed and the position of the float is checked. If a sufficient amount of oil is stored, an upward force derived from oil buoyancy is larger than a downward force of the own weight of the float, from among the forces that act on the float. The float thus protrudes beyond a large-diameter portion upon removal of the float cap from the float guide.