Today, it's common practice to use a cylinder leak down gauge to evaluate how well each cylinder performs in retaining pressure.

Mityvac’s compression tester is unique in this list for including an air-hold adapter that you can use to effect valve seal repairs without having to remove the engine’s cylinder head.

When you bring your vehicle in for a compression test, a mechanic places a gauge into each of the cylinders to read how much pressure the engine is producing when the engine turns over.