slant 6 oil weight

A multi-grade oil (like 10W-30) means that it has the flow of a 10W-grade oil when cold and the flow of a 30-grade oil at 100°C/212°F. A single grade oil (like SAE 30) will be thicker (more viscous) than a multi-grade when colder than 100°C and will be thinner (less viscous) when hotter than 100°C. That is, a multi-grade oil has a flatter viscosity curve than a single grade oil.