What type of oil is recommended for 2-cycle Diesel motors?

The recommendation for 2-cycle Diesel motors is to use a specific type of oil that suits the engine's operational demands. The option that refers to 40w-STR is correct because 2-cycle Diesel engines operate at higher temperatures and depend on oil that maintains its viscosity under these conditions. This specific formulation is designed to provide better lubrication and protection against wear and tear, especially in high-performance situations commonly encountered by Diesel engines.

Typically, oils designated with a “STR” (which stands for "super thermo-reduced") are formulated to resist the breakdown that can occur in extreme temperatures, making them ideal for 2-cycle Diesel applications. The viscosity grade ensures that the oil flows adequately at lower temperatures while still providing sufficient thickness to protect the engine at operating temperatures.

Other oils listed may not provide the same level of performance or protection at the temperature ranges experienced in 2-cycle Diesel motors, making the selected choice the most suitable for these engines.