Oil companies developed multi-grade oils in the 1940s. These oils, like SAE 10W-30, meet both low- and high-temperature grade specifications. By adding Viscosity Index Improvers (VII), which are large oil-soluble polymers, the oils resist thinning as they heat up. For instance, a 10W oil thins to about 5 cSt at operating temperature, but with VII,
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The SAE J300 Engine Oil Viscosity Classification provides a standardized way to categorize oils based on their viscosity at different temperatures, helping consumers and manufacturers choose the right oil for specific applications and climates. In 1911, the Society of Automotive Engineers (SAE) introduced the SAE J300 Engine Oil Viscosity Classification, a numerical code system designed