Why does the old Mazda 6 use 5w40 engine oil?

[OBrantley]

Because 5w40 engine oil provides better protection for the engine. Here is relevant information about 5w40 engine oil: 1. In 5w40 engine oil, 'w' stands for winter, indicating it is suitable for winter use. The '5' before the 'w' represents the viscosity at low temperatures, with a smaller number indicating better fluidity and cold resistance. The '40' refers to the viscosity at 100 degrees Celsius, with a higher number indicating greater viscosity and better high-temperature resistance. 2. The functions of engine oil include: reducing friction and high temperatures; cooling and lowering temperature; cleaning; shock absorption; and preventing rust and corrosion. 3. Engine oil, also known as engine lubricant, is composed of base oil and additives. The base oil is the main component of the lubricant, determining its basic properties, while the additives compensate for and improve any deficiencies in the base oil's performance.