Performance Tool Flex Drive Compression Tester

When an engine starts losing power or misfiring on a cylinder, a compression test tells you whether the rings, valves, or head gasket are the issue. The Performance Tool W80579 makes that job easier with an 11-inch flexible rubber hose that reaches spark plug holes in tight engine bays where a rigid tester would be difficult to thread in.

The gauge reads from 0 to 300 PSI and includes an air-hold valve that locks in the highest reading until you press the reset button. This means you can crank the engine, walk over, and read the result without rushing. The hose unscrews from the gauge body, so you can thread it into the plug hole first and then attach the gauge, which is helpful when access is limited. Adapters for both 14mm and 18mm spark plug threads are included, covering the vast majority of gasoline engines on the road.

Complete instructions come in the box. For anyone diagnosing a rough-running engine at home, this tester gives you a clear cylinder-by-cylinder picture without a trip to the shop.