Mineral transformer oil density is often roughly 860 to 900 kg per cubic meter at a reference temperature, with density decreasing as temperature rises. Ester fluids can be higher than mineral oil, and silicone fluids have their own range. Because density affects tank volume calculations, shipping weight, and spill containment sizing, operators should use the specific product datasheet value and apply temperature correction if the oil is significantly warmer or colder than the reference condition. Field measurements should note temperature when reporting density.
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