What happens when the thermostat gets stuck open?

When a thermostat gets stuck open, it prevents the engine from reaching its optimal operating temperature. This situation leads to the engine running cooler than it should, which directly affects its performance. A cooler engine does not vaporize fuel as efficiently, which can result in incomplete combustion and ultimately decreased fuel efficiency. Consequently, the vehicle may experience poor gas mileage as more fuel is required to maintain performance, yet the inefficient burning of fuel means that less of it is converted into usable energy.

This condition can also lead to other issues over time, such as increased engine wear due to the engine not reaching the ideal temperature, which is crucial for efficient operation and emissions control. This is why the outcome of a stuck open thermostat primarily results in an engine that runs cold, leading to reduced fuel efficiency.