What is transformer oil density and how does temperature affect it?

Transformer oil density is the mass per unit volume and it decreases as temperature increases because the oil expands. This matters for volume calculations, conservator sizing, oil level indications, and logistics such as transport and tank filling. Density also influences buoyancy driven oil circulation in natural cooling modes. Specifications usually list density at a reference temperature, often 15 degrees Celsius, and provide correction factors or charts. For accurate operating condition estimates, use the supplier data sheet and apply temperature correction.