Lisle Compression Tester Kit 0–300 PSI / 14mm & 18mm Adapters — Analog Gauge for Gasoline Engines

The Lisle 20250 Compression Tester is a handheld gauge kit that lets you quickly and accurately read cylinder compression on gasoline engines, displaying results in both PSI and kPa and fitting common 14mm and 18mm spark plug ports.

When diagnosing engine performance, a reliable compression test is one of the fastest ways to identify worn rings, leaking valves, or head gasket issues. The Lisle 20250 provides a clear analog gauge that reads 0–300 PSI (0–2100 kPa) and includes adapters for two common spark plug thread sizes so you can test most passenger cars, light trucks and small engines without extra tools.

How does the Lisle 20250 make compression testing easier?

The Lisle kit simplifies the process with a direct-mount gauge and two adapter fittings so you can hook up to a spark plug hole and crank the engine to record peak pressure. Its wide scale and dual-unit markings reduce guesswork and let you compare readings against manufacturer specs.

• Clear 0–300 PSI and 0–2100 kPa markings for quick interpretation.
• Included 14mm and 18mm adapters fit most gasoline cylinder heads.
• Handheld gauge body and hose allow accessible connections in tight engine bays.
• Durable construction tolerates shop use and repeated testing.

What measurements and units does the gauge display?

The Lisle 20250 displays both imperial and metric units so you can read compression in PSI or kilopascals without conversion. The instrument covers the typical automotive compression range up to 300 PSI, which suits most gasoline engines used in light vehicles and equipment.

• Scale range: 0–300 PSI—visible, graduated increments for accuracy.
• Metric scale: 0–2100 kPa printed on the same dial for instant cross-reference.
• Analog needle display shows peak pressure recorded during cranking.

Which engines and spark plug sizes will it fit?

This tester includes fittings for 14mm and 18mm spark plug threads—the two most common sizes on passenger cars, many light trucks and small engines. The adapters let you test cylinders without buying additional threaded fittings.

• 14mm adapter for many modern passenger cars and motorcycles.
• 18mm adapter for older or larger spark plug ports and some small engines.
• Universal hose and quick-connect arrangement for straightforward hookup.

How should I use the Lisle 20250 safely and effectively?

Follow basic engine-test precautions: disable ignition, remove fuel injectors or disable fuel supply, and crank the engine with the throttle wide open. Record pressure from each cylinder and compare to the manufacturer's specifications; consistent low readings or large variances indicate mechanical issues.

• Always disable ignition and fuel when testing to prevent backfire or starting.
• Crank the engine several compression strokes to allow the gauge to reach peak reading.
• Note results per cylinder and perform a wet test if readings are uniformly low to isolate rings versus valves.

Who is this for? The Lisle 20250 Compression Tester is designed for DIY mechanics, independent repair shops, fleet technicians and automotive hobbyists who need a dependable, easy-to-read compression gauge for routine diagnostics and troubleshooting. It’s a compact, cost-effective tool for anyone who performs engine health checks on gasoline engines that accept 14mm or 18mm spark plug fittings.