Which transmission issue often leads to increased fuel consumption?

Slipping clutches in an automatic transmission can lead to increased fuel consumption because they disrupt the efficient transfer of power from the engine to the drivetrain. When clutches slip, the engine must work harder to maintain the desired speed, which results in more fuel being burned than necessary. This inefficiency can cause the engine to operate outside its optimal performance range, leading to a higher fuel-to-air mixture being utilized, consequently increasing overall fuel consumption.

The other issues listed can impact the performance of the vehicle, but they do not directly affect fuel consumption as significantly as slipping clutches do. For example, dirty fluid can harm the operation of the transmission, but it typically does not produce the immediate drastic effects on fuel economy like slipping clutches. Similarly, worn bearings and malfunctioning filters can lead to various performance problems but do not have the same direct correlation with fuel consumption as clutch slippage does.