Your car's engine compression can tell you a lot about the overall health of the engine. If your car is blowing blue smoke out of the tailpipe, or if your car is losing lots of oil, you could have a bad piston ring. This will also cause low compression in that cylinder, and a compression test will tell you. The same goes for a bad valve. Even if you are just noticing a general lack of power, a compression test can help you rule out some of the more serious possible causes. *Note: This test was performed on an ancient Porsche engine to demonstrate the basics of how a compression test works. Please consult your repair manual for specific instructions on your vehicle.
Compression:
Definition: In internal-combustion reciprocating engines, the squeezing of the fuel-air mixture in the cylinder of a spark-ignition engine or the squeezing of the air in a diesel engine. Compression makes combustion more effective and increases engine efficiency.
