In relation to cars, PSI stands for pounds per square inch. PSI is a unit of measurement for the pressure within a vacuum system, such as car tire inflation or engine compression levels.
Depending on the type of car and purpose of the tire, manufacturers specify the recommended PSI range for proper performance. Under-inflated tires are problematic, since they not only increase the rate at which tires wear out, but also reduce the car’s fuel efficiency. Conversely, over-inflated tires can be extremely dangerous. As the tires spin and warm up, the air inside them expands. If the tires are over-inflated prior to use, the air expansion may cause the tires to burst. For this reason, it is very important to routinely check the air pressure of tires to ensure they are within the recommended manufacturer’s range.
In relation to the engine, PSI refers to the compression generated by the engine as a whole. A compression test is a great way to determine whether the engine is performing as it should. Proper functioning engines should have a compression over 100 PSI per cylinder. If a car engine’s compression is below 100 PSI, it is possible that the engine’s valves, valve seats or piston rings are worn out.