Definition
The temperature at which dissolved wax in a petroleum-based fuel or oil begins to separate out and form a visible cloudy haze as the liquid is cooled.
Plain English
The temperature at which a fuel or oil starts to look cloudy because tiny wax particles are beginning to come out of the liquid as it gets cold.
Context Anchor
Seen in fuel and oil specifications, cold-weather operating discussions, and maintenance information for petroleum-based fluids.
Derivation
Named for what you actually see: as the liquid cools, wax crystals form and the fuel takes on a cloudy appearance. The 'point' is simply the temperature at which that cloudiness first appears.
Why Pilots Care
If the fuel temperature drops below the cloud point, wax can clog filters and lines, restricting fuel flow to the engine.
Grounding Statement
Picture a clear fuel sample on a cold ramp slowly turning hazy as the temperature drops.
Intuition Check
Cloud point does not mean the temperature where weather clouds form. It also does not mean the fluid is fully frozen; it means the first visible cloudiness appears in the fluid.
Example Sentence 1
Before a winter flight at high altitude, the operator confirmed that the jet fuel's cloud point was well below the coldest temperature expected during the trip.
Example Sentence 2
Fuel with a higher cloud point may need additives when operating in very cold conditions.