Engine Compression Tester: Is It Worth Buying?


Apr 29th, 2022

Engine Compression Tester: Is It Worth Buying?

Engine compression tests can tell you a lot about your engine’s internal state. However, you can only perform such a test if you have the necessary equipment. Yes, engine compression tester kits are widely available, but are they worth spending on?

Engine compression testers are worth buying if you plan on using them regularly, say, you’re managing a fleet of vehicles or are working on several cars. For a one-off engine compression test, you can pay your mechanic a small fee to do it instead—it will be so much cheaper.

This guide will help you decide whether buying an engine compression tester is a good idea or just a waste of money. 

You’ll discover what information you can get from such a test and learn the pros and cons and what comes with a typical compression test kit.

What Does a Compression Test on an Engine Tell You?

Let’s start this guide by understanding what an engine compression test is all about.

A compression test is a way of checking the internal conditions of your engine. The test helps you determine if your engine’s valves, valve seats, and piston rings are in good shape.

Setting Up the Engine Compression Tester

As the name suggests, the test measures the compression levels inside the engine. You do that by putting an engine compression tester in the place of a spark plug to test one cylinder at a time.

With the tester in place, the engine is then spun through its cycles to create pressure in that cylinder. Then, the test records the highest point displayed on the compression tester gauge.

By comparing the maximum compression levels of all the cylinders in your engine, you can also tell whether the parts are wearing out evenly or one cylinder is experiencing more wear than others.

Engine Compression Test Readings

Engine compression test results are expressed in pounds per square inch (PSI). Those readings will help you understand each engine valve’s condition. When you find the PSI readings too low, you can then get the engine the help it needs. 

What Are the Pros and Cons of an Engine Compression Test?

Now that you know what insight an engine compression test can offer you, the next big question to ask is whether you would want to perform such a test yourself. 

By understanding the pros and cons of compression testing, you’ll be able to make better-informed decisions about investing your hard-earned money in a compression tester.

So, here’s the good and bad about this form of testing:

Benefits of Engine Compression Testing

  1. Widely accepted test: First and foremost, engine compression testing is a widely known, understood, and used method of testing your engine. In other words, this isn’t a niche kind of testing reserved for experts, so there’s plenty of information about it out there.
  2. Common testing tool: Because compression testing is so widely accepted, the tools you use (i.e., the testers) are also widely available. You can pick up a testing kit at your favourite auto parts and accessories store. 
  3. Different style testers: Compression testers also come in two styles. First, you have screw-in and hand-held types available. That means you can do a bit of experimenting and buy a tester that suits your preferences.
  4. Location independent: The beauty of compression engine testing is that you can do it anywhere. You won't have to be anywhere near a compressed air source to get the job done.

Drawbacks of Engine Compression Testing

  1. Not foolproof: Despite how common and well-known engine compression testing is, the process isn't foolproof. So, incorrectly performing the test could give you a reading that shows the cylinder's maximum pressure is too low. Unfortunately, there's no way to verify the results except to ensure that you're performing the test properly.
  2. Interference by battery or starter: The compression necessary for this test is done by cranking the engine. However, a weak battery or faulty starter motor could produce a low cranking speed. That will lead to the tester showing a low reading.
  3. Incorrect throttling: Lastly, engine compression testing will only give accurate results when the throttle is held in the wide-open position. If that doesn’t happen for whatever reason, the test can also produce another false negative

What’s in an Engine Compression Test Kit?

An engine compression test kit will have all the parts you need to perform the test yourself. 

The most crucial part of any kit is the gauge which will show you the pressure readings of each engine valve you test. Some gauges can go up to or beyond 300 PSI, allowing you to test a wide range of different engines.

Aside from a gauge, test kits also come with helpful accessories like:

  1. Adapters: Push-in or screw-in adapters allow you to connect the gauge to various engines (e.g., straight, angled, etc.)
  2. Extension hoses: Kits also come with extra-long hoses to use on engines with hard-to-reach parts. That way, you can connect the gauge and perform the compression test much easier.
  3. A storage case: All the parts mentioned above need to stay in a sturdy case, which most kits come with as a standard accessory.

Whether you’re looking for a petrol engine compression tester or a diesel engine compression tester, you can check with your local auto supply or shop online to find a kit you like.

Bottom-Line: Is Buying an Engine Compression Tester Worth It?

Should you invest in an engine compression tester?

Well, it depends. This article shows that engine compression testers are pretty standard, and almost every auto workshop should have a tester available. 

If you plan to do a one-off engine compression test, or perhaps one every year, buying a test is not worth it. You could always drive to your preferred workshop, which can then conduct the test for you.

However, if you manage a fleet of vehicles or plan on performing engine compression tests often, then perhaps buying a tester would be worth it.

Under those circumstances, buying your own tester will save you money in the long run.

If you want more info about engine compression, please check out CarPartAU for more helpful articles. You may also use the Directory to find the best auto workshops in your area or find an auto parts store that sells engine compression test kits.

By Ray Hasbollah