Which of the following statements about piston rings is incorrect?

Piston rings are critical components in an engine, and their proper installation and orientation can significantly affect performance and longevity. The statement suggesting that rings are installed using a ring compressor is indeed misleading. While a ring compressor is commonly used when installing the piston and its rings into the cylinder bore, it does not mean that the rings themselves are installed using the compressor in the traditional sense. The rings are typically placed onto the piston by hand, often with lubrication to ease the process before the assembly is inserted into the bore.

Each of the other statements accurately reflects best practices in working with piston rings. Measuring the ring end gap is crucial to ensure there is appropriate clearance for thermal expansion during operation. Installing rings in the correct vertical direction is vital as misalignment can lead to increased wear or even failure. Additionally, staggering the ring end gaps is an accepted practice to prevent excessive blow-by, as it helps to reduce the leakage of combustion gases past the rings. Therefore, while the use of a ring compressor is relevant to piston installation, the specific claim about the installation of the rings themselves is not accurate, making it the incorrect statement in this context.