When is high oil filter differential pressure most likely to occur?

High oil filter differential pressure occurs when there is a significant obstruction in the filter that restricts the flow of oil. This condition is most likely to arise with a clogged filter. As oil passes through the filter, the accumulation of contaminants can lead to a buildup that restricts the flow, causing the pressure differential across the filter to increase.

If the filter becomes too clogged, the oil may struggle to flow through, leading to elevated pressure readings. Proper filtration is essential for maintaining system efficiency, and when the filter is compromised, it can impact the performance of the entire lubricating system.

In contrast, the other options may not be directly related to differential pressure increases in the same way. For example, an oil change generally involves replacing the old filter and oil, which initially may not cause any pressure issues. Bypassing the filter typically prevents any differential pressure from building up, as oil flows directly without being filtered. Cold weather starts can lead to increased viscosity, but they don't consistently result in high differential pressure unless the filter is significantly obstructed.