Fluid Properties Explained, Part 7:
TipSheet™ is a service of Paratherm — Heat Transfer Fluids. The details are applicable to all heat transfer fluids in closed or vented hot-oil systems.
As the quality of motor oil has improved over the last 15 years, so has the quality of petroleum based (mineral oil) heat transfer fluids.
The old way to refine oils — solvent dewaxing — has given way to hydrotreating, which, while more expensive, produces oils that have almost no residual sulfur compounds or asphalt molecules. With no impurities present to start the fluid degradation process, the new oils have much longer service lives and can operate at higher temperatures.
How can you tell the difference? Color.
Impurities give oil a yellow color – the darker and less transparent, the more impurities are present. Yellow may be cheaper to buy but it’s not cheaper to own. So the next time you’re shopping for mineral-oil based fluid, ask for a sample from each potential supplier. Pour each one into a glass jar and compare. If it’s the color of beer, it’s old technology.