5W-20 vs 5W-30

5W-20 and 5W-30 share the same winter-grade number but differ in their high-temperature viscosity grade. That difference can matter for oil pressure, friction, fuel economy, and engine design.

What they share

Both oils meet the same SAE 5W winter-grade requirements. That does not mean their cold behavior is identical in every formula, but they belong to the same winter grade.

Where they differ

At operating-temperature test conditions, a 30-grade oil has a higher viscosity range than a 20-grade oil.

Why engines specify a grade

Bearing clearances, oil pump design, variable valve timing, turbochargers, emissions systems, and fuel-economy targets all influence the oil specification.

Do not choose by thickness alone

Use the viscosity and performance specification in the owner's manual. Some engines approve more than one grade for certain temperatures, while others are more specific.

Quick checklist

Use the product label, manufacturer directions, and the specific requirements of your situation. Compare the complete product or system rather than making a decision from one marketing phrase, ingredient, or number.