How would I know if my car bushings need to be replaced?

Car bushings are prone to damage due to the material used in their production. Liquids can be detected in the bushings of some vehicles. The engine mounts and the subframe are in the same boat.
The bulk of vehicle components are comprised of rubber, which wears out over time. When that time comes, the rubber shell cracks and leaks fluids.
Check MOT status of your vehicle and replace any damaged or worn bushings. The reason for this is because over time, vehicle bushing parts wear down and fail, resulting in a range of driving issues. This is not only a MOT failure, but also exceedingly dangerous because you might lose control of your car while driving.