Final answer:
Allowing your vehicle to run unnecessarily while stopped or parked can waste fuel, contribute to air pollution, and cause unnecessary wear and tear on your vehicle's engine.
Step-by-step explanation:
When you allow your vehicle to run unnecessarily while stopped or parked, it has several consequences. First, it wastes fuel, which can be expensive and harmful to the environment. Second, it contributes to air pollution by emitting greenhouse gases and other harmful pollutants. Third, it can cause unnecessary wear and tear on your vehicle's engine, reducing its lifespan and potentially leading to costly repairs. It's best to turn off your vehicle's engine when it's not in use to save fuel, reduce pollution, and preserve the longevity of your vehicle.