Question 67 UFIV01 - Chief Engineer - UFIV

The Correct Answer is A **Explanation for Option A (Correct Answer):** Option A, "All Proof 10W50 (Polyolester)," is the correct choice because, based on standard oil charts for engine governors (like Illustration MO-0161, which is commonly used in marine engineering contexts), Polyolester-based synthetic oils offer the widest acceptable operating temperature range suitable for precision components like speed control governors, especially when compared to other synthetic bases. For the required ideal operating range of $130^{\circ} \mathrm{F}$ to $205^{\circ} \mathrm{F}$, a high-performance Polyolester formulation like All Proof 10W50 typically provides a stable viscosity and film strength throughout this entire band and beyond, ensuring adequate lubrication and reliable governor operation. In many marine specifications, Polyolester is the preferred base stock for high-temperature and critical low-temperature applications due to its excellent thermal stability and resistance to shearing. **Explanation for Other Options (Incorrect):** * **B) Amsoil 10W40 (Diester):** While Diester synthetics offer good performance, they are generally not approved or recommended for the same wide range or critical applications as Polyolester in governor systems, particularly concerning thermal stability at the higher end of the operating range, or they might not meet specific OEM viscosity requirements for this application as effectively as the specified 10W50 Polyolester. * **C) Mobil 1 (Synthesized Hydrocarbon):** Synthesized Hydrocarbons (like PAOs) are excellent general-purpose synthetics. However, in sensitive governor systems, they often have a slightly narrower acceptable temperature range or inferior thermal stability compared to Polyolester bases, especially in applications subject to high heat soak or rapid temperature changes. They may not be considered the "best" or "most capable" choice for this specific critical temperature range. * **D) DN600 (Hydrocarbon):** DN600 is a conventional or semi-synthetic hydrocarbon-based oil. Standard hydrocarbon (mineral) oils have a significantly narrower ideal operating temperature range and lower thermal stability than true synthetics (Polyolester, Diester, PAO). They would likely thin out too much at the $205^{\circ} \mathrm{F}$ mark or break down prematurely, making them inadequate for providing reliable lubrication across the required $130^{\circ} \mathrm{F}$ to $205^{\circ} \mathrm{F}$ ideal operating band for a precision governor.