When the **tire inflation pressure is lower than recommended**, the vehicle **consumes more fuel**. This happens because:

- **The tire deforms** and heats up more than normal, which increases rolling resistance. This greater resistance means the engine needs more energy to move the vehicle, thus increasing fuel consumption.

- Additionally, a tire with low pressure is less efficient, as it does not roll optimally on the road, which also contributes to higher fuel consumption.

Therefore, it is important to maintain the correct inflation pressure to ensure efficient fuel consumption and improve the vehicle's stability and safety.