A 5W-30 Is Not One Exact Viscosity
This is one of the most important things to understand about oil grades.
An SAE 30 does not have one exact viscosity.
It has to fall within a defined viscosity range.
That means one company’s 5W-30 can be slightly thinner or thicker at operating temperature than another company’s 5W-30 while both still meet the requirements of SAE 30.
Organizations such as the SFI Foundation, the FIA and the Snell Memorial Foundation establish performance standards for motorsports safety equipment. These standards are not simply product grades or marketing levels. They establish test requirements for impact protection, fire resistance, material strength, hardware performance and other hazards encountered in racing.
For most daily-driven vehicles, a quality motor oil that meets the manufacturer’s required viscosity and specifications can provide adequate protec...