Understanding Oil Specifications — What They Really Mean

Close-up of engine oil specification sheet showing viscosity and certification ratings
Know exactly what your engine oil specs mean and how they impact performance, protection, and reliability

When it comes to engine protection, oil specifications matter just as much as the oil itself. From API and ACEA to ILSAC and OEM-specific ratings, these classifications aren't just technical jargon—they define how well your oil performs under pressure. Whether you're running a high-mileage work truck, a performance car, or heavy-duty equipment, understanding these specs can mean the difference between long-term reliability and premature wear. On this page, Vyscocity breaks down what each spec means, why it matters, and how to choose the right oil with confidence.

OEM Oil Specifications

Chrysler MS-A0921

A performance specification used in many Chrysler, Dodge, Jeep, and RAM vehicles. It focuses on deposit control, wear resistance, and oil stability under heat and load. Oils meeting MS-A0921 are often synthetic and designed for extended oil change intervals.

GM dexos R

GM dexos R – Required for newer GM engines; emphasizes oxidation resistance and deposit control. AMSOIL Signature Series is fully dexos R-compliant.

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