What effect does internal leakage in a fuel/oil heat exchanger downstream of the HP fuel pump have on the oil level?

When considering the impact of internal leakage in a fuel/oil heat exchanger downstream of the high-pressure fuel pump, it's important to understand the flow dynamics involved. In this scenario, internal leakage refers to the unintended flow of oil that escapes from one side of the heat exchanger and enters the other side, rather than flowing through the intended pathways.

If internal leakage occurs, it means that oil is moving out of the intended circuit, which would typically be contained within the oil system. This leakage effectively allows more oil to remain in the heat exchanger rather than returning to the oil sump or reservoir. As a result, the accumulation of oil in the heat exchanger causes the overall oil level in the system to rise, as there is more oil present than what is typically accounted for in the normal operation of the system.

By understanding the flow dynamics of the fuel and oil, it's clear that the internal leakage contributes additional oil to the heat exchanger, creating a higher oil level than expected. Therefore, the correct conclusion is that this leakage would cause the oil level to rise.