What could lead to a sudden increase in heating oil usage?

A leak in the heating oil system would directly result in a sudden increase in heating oil usage due to the compromised integrity of the system. When a leak occurs, the heating oil escapes the system instead of being used effectively to heat the space. Consequently, the system may require more frequent refilling to maintain the desired temperature, leading to an increase in overall oil consumption. This unintended loss can become significant depending on the severity of the leak, thus causing a noticeable spike in usage.

In contrast, a decrease in ambient temperature would naturally increase heating demand but would not necessarily lead to an unpredictable surge in oil usage in the same way a leak would. Similarly, a malfunctioning thermostat could result in inefficient heating, but it wouldn’t specifically cause an immediate increase in oil usage; it might actually lead to fluctuations or a steady use of oil. On the other hand, a higher efficiency burner is designed to optimize fuel usage, which would typically decrease rather than increase heating oil consumption.