Multi-grade oils, which are the standard today, use additives called viscosity index improvers to allow the oil to behave as a 5W-30 across a massive temperature range. The number preceding the "W" is a measure of the oil's viscosity during cold starts.
What Do Numbers In Oil Mean Grade
Consequently, the numbers on a modern synthetic bottle represent a much broader and more reliable performance window than their older counterparts, allowing the engine to operate optimally in diverse conditions. These synthetics often outperform traditional oils because they maintain their viscosity more consistently, providing better protection in both extreme heat and cold.
The High-Temperature Rating Explained While the "W" rating ensures the oil behaves in the cold, the second number—such as the "30" in 5W-30—indicates the oil's viscosity measured at 100°C (212°F). Conversely, using an oil that is too thick (a higher viscosity) can reduce fuel economy, hinder cold starts, and slow down oil circulation, which can starve the engine of lubrication during crucial moments.
What Do Numbers In Oil Mean Grade
The Meaning of the Viscosity Grade The primary set of numbers, such as the "5" in 5W-30 or the "30" in the same grade, refers to the oil's viscosity, or its resistance to flow. The system uses a sliding scale where lower numbers indicate thinner oil that flows faster, while higher numbers represent thicker oil that resists breakdown under heavy load.
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