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Published Sep. 30, 2021

When it comes to automotive work, there are a few procedures that are universal to all applications. Though the specifics of how the job is performed may vary, the core fundamentals carry over. One job that all applications with an internal combustion engine will be subject to at one point or another is a compression test. This simple test takes a reading of the pressure inside the combustion chamber, telling us quite a bit about the overall health of an engine. On some applications, it can be a total pain. Sometimes, the spark plug holes are all easily accessible, while others might require you to drop the exhaust manifolds or headers to get to work. We might not know exactly what you’re in store for, but we do know that picking the right tool can go a long way. So much so that you might only ever need to buy one. That’s why we want to give you a buying guide for compression testers. Before we do that, we’re going to showcase some of our top picks on the market.

Best Compression Tester Reviews & Recommendations

Positive praise surrounding accuracy and reliability are hard to ignore when a kit is so well-equipped. We’re kicking off our list with a favorite by many gearheads. OTC is known for supplying quality specialty automotive tools at relatively affordable prices. With a track record in this division, it’s no surprise to see that they are on the ball with compression testers. This particular kit comes with an analog compression tester, a solid selection of flexible attachments, and three different thread adapters to cover most common spark plugs. As for accuracy, it seems that the gauge is above average, and the quality ensures you’ll have this set around for years to come. An excellent detail about this particular set is that it comes with a pretty solid storage case with detailed directions on how to properly use the tool.

While this set has a rather positive reputation, there are some complaints we should address. It seems that this tool is subject to quality control issues that occasionally net problems with fit to spark plug holes. We will point out that the system is reliant on threaded attachments all the way around, which can make setup a pain. Also, it does seem that it’s somewhat easy to accidentally break the seal on threads as you work.

Specs
  • Manufacturer OTC
  • Part Number 5605
  • Gauge Type Analog
PROS

Accurate and reliable

Comes with a good selection of attachments

Storage case included

CONS

Quality control seems to be an issue

Threaded fittings can be a hassle

Seal tends to break while working

Despite the low price, this kit offers respectable performance and attachments that cover most needs. We won’t pretend like we don’t use the more affordable stuff when it comes to specialty tools. After all, there’s a lot of great stuff out there that you can save money on. If you need an affordable compression tester this is one of your best bets. This kit comes with an analog compression tester, a total of four thread adapters, and two rubber cone attachments for quick jobs. Everything also fits neatly into the included carrying case. Perhaps what makes this set stand out among others is the use of quick-connect fittings. This type of fitting allows you to thread into the spark plug holes and quickly snap the gauge in place, making it very easy to get to work.

While this is a respectable kit for the money, there are some issues. There is a lot of praise regarding the value and decent performance, but accuracy is often an issue. We can link inaccuracy to quality control concerns, but the tool does seem to be relatively short-lived, which can indicate overall quality is questionable. Still, it’s a decent tool to pick up for quick jobs.

Specs
  • Manufacturer Betooll
  • Part Number HW0130
  • Gauge Type Analog
PROS

Affordable price point

Comes with a wide range of attachments

Relies on quick-connect fittings

Storage case included

CONS

Accuracy is questionable

Quality control seems to be an issue

Relatively short lifespan

The high-quality accuracy and dependability are what you demand, everything this set includes is a fantastic bonus. Mityvac is always a solid brand to turn to for specialty automotive tools. That’s especially true when you need a tool that brings certain functions to the table that others do not offer. This particular compression tester stands out among most digital offerings due to its accuracy, durability, comprehensive range of attachments, and use of quick-connect fittings. Quick-connect fittings are always a major deal because they will make setting the tool up far easier than if you rely solely on threaded connections. The quality of this set is evident throughout, however, the case really captures our attention. It’s a lot more robust than others, and you can certainly count on it and its contents for years to come.

The cost is a little higher than others, but not so much so that the expense isn’t justifiable. However, it is worth mentioning that use with small engines seems to be something of an issue for the tool. It also seems that, while everything else is resilient, the gauge itself should be handled with care as it damages somewhat easily.

Specs
  • Manufacturer MityVac
  • Part Number MV5532
  • Gauge Type Digital
PROS

Digital display is easy to read

Comes with a wide range of attachments

Relies on quick-connect fittings

High-quality construction

CONS

Accuracy on small engines is questionable

Digital gauge is easy to damage

Overall performance is solid and the reinforced hose helps it stick around. Throwing a set of headers on an old-school engine is one of the first upgrades you make. They offer some major improvements over stock but can be a nightmare to work around. If you can run a compression tester with the headers in place, this is the one to consider. We say that because it features a reinforced braided steel hose that connects the gauge to your cylinders. It certainly won’t fray or burn up quite as easily as many others. On top of that, it offers the kind of accuracy you can depend on and relies on quick-connect fittings to keep the setup simple. Also, it’s worth pointing out that it comes with a decent selection of thread adapters and a rubber cone connection for those quick jobs.

One thing that you absolutely need to know before buying is that this does not come with a storage case, despite what the price might suggest. Furthermore, it does seem that the rubber seals between connections do seem to fail prematurely, and the lack of extensions limits this to use on certain vehicles.

Specs
  • Manufacturer Equus
  • Part Number 3614
  • Gauge Type Analog
PROS

Reinforced hose resists heat and sharp edges

Includes a solid range of adapters

Relies on quick-connect fittings

CONS

Does not come with storage case

Limited number of attachments

Seals between attachments are questionable

It’s affordable, built-well, and accurate — there’s no ignoring it. We’re wrapping up our list with an entry from yet another brand DIYers have depended on for years. You’ll find the Lisle name on the shelf of most parts stores because it offers quality tools at affordable prices that will stick around for years to come. This compression tester is no exception. The analog gauge is accurate and will stay in the game for a surprisingly long time, despite the low price. Furthermore, the hose and attachments are no slouches either. They fit well and are sure to withstand abuse. We’ll even tip our hat to the fact that Goodyear manufactures the rubber used for the hose on this compression tester.

While you can depend on this tool, it’s rather limited in comparison to other entries. It does not come with many attachments at all. In fact, it only works with 14mm and 18mm threads, meaning the equally as common 10mm and 12mm adapters must be purchased separately. Also, it does not rely on quick-connect fittings, which does make setting up something of a hassle.

Specs
  • Manufacturer Lisle
  • Part Number 20250
  • Gauge Type Analog
PROS

Affordable price point

High-quality construction

Accuracy surpasses expectations

CONS

No attachment included

Some adapters must be purchased separately

Does not use quick-connect fittings

How We Selected The Products 

Compression testers do an incredibly important job. So much so that there are few other tools that make life quite as simple when it comes to determining the health of your combustion chamber without tearing the engine apart. That said, it’s important you get the right one to prevent any headaches. 

When putting our list together, we evaluated a few key characteristics. The first being quality and overall reliability of the parts used. Accuracy is another key detail we made sure to keep an eye on. After all, what’s a measurement tool worth if it’s not accurate? After that, we took the time to read into features and functions that make the tool useful and versatile enough to cover a good range of applications. That way, we can ensure we have something for everyone. 

Our product selections, rankings, and awards for this story are based on research. While we haven’t conducted real-world testing on all of these products yet, we’ve looked at consumer testimonials and data, tutorials, and general discussions on social media and in forums. We also consider price and specification in the context of the segment. And, of course, we rely on our institutional knowledge of the automotive landscape to weed out weak products.

Buying Guide/What to Look For 

What if we forgot a detail that makes a compression tester work for your application, or you don’t like the brands we’ve leaned on? No problem. That’s what this buying guide is for. It’s here to give you some more insight into how we made our selection and help you hone in on the compression tester that best suits your needs.

What to Consider When Buying Compression Testers 

Types of Compression Testers 

Alright, so first things first, let’s talk about some of the different types of compression testers on the market. They all tell us how much pressure is in the chamber; only how they tell us varies. It’s important that you pick which you feel most comfortable using, as this information is incredibly valuable. 

Analog

We’re dealing with pressure, and an analog compression tester simply uses a sweeping dial gauge to tell us that information. This type of gauge has the benefit of reliability in its corner. Though it’s simple, it’s reliable and cheaper to manufacture correctly than the alternative. In other words, it’s usually the safest route to take. The only drawback is that analog dials aren’t quite as convenient to read as their digital counterparts. 

Digital 

If you don’t like analog gauges, digital compression testers are available to you. Rather than having to translate the info a dial gauge is providing, the digital display gives you a direct numerical reading of cylinder pressure. These are incredibly convenient, but they aren’t perfect. Cheaping out in manufacturing can impact accuracy, and there is a dependency on batteries. However, picking a model from a reliable brand and keeping spare batteries on hand will prevent headaches. 

Whistle 

Unlike digital or analog compression testers, whistles generate noise to translate information. No, they don’t shout the reading out for you, but the pitch of the whistle tells you the health of your cylinders. This is handy in many cases where a gauge isn’t necessary or isn’t an option, and they are sometimes included along with your primary compression tester. As quick as they can be to set up and use, discrepancies are obviously an issue as this type of tester provides no documentable date. 

Compression Tester Key Features

Once you select the type of compression tester you want to use, it’s time to hash out some of the details. These three key features are all pretty simple. Still, they go a long way in ensuring that the compression tester will work for you.

Accuracy

Accuracy should be your primary concern. Now, there is room for some discrepancy in any case, but you still need a tester that can provide repeatable readings. Without this ability, all of your hard work can be in vain, and you might end up chasing problems that simply don’t exist. 

If there are any tools that you should spend good money on, it’s measurement tools. However, there are a lot of good and affordable compression testers out there. Doing the homework and reading what others have to say is the best way to track them down. 

Proper Attachments 

Ensuring the compression tester will tap into your engine is essential. They do so by threading into the spark plug holes, and you do need to make sure the proper adapters that match your engine’s thread type are included. 

Thread types shouldn’t be your only concern, though. Some compression testers come with quick-fittings and other attachments that are essential on some applications. It’s important that you consider your approach and which additional attachments and installation process are best for you. 

Quality Construction

At their core, compression testers are pretty simple. That doesn’t mean there’s much room for cheap parts, though. They’re subjected to rigorous environments and need to function consistently. That means you really do want a compression tester that can stand up to the task at hand. 

Blindly dropping money on expensive tools will only get you so far. Gimmicks and the name stamped on the side may be all you’re paying for. Take the time to read the reviews and determine if the quality is there and that the compression tester you’re considering is worth your money. 

Compression Tester Tips and Tricks

Now that you’re just about ready to pick out a compression tester, let’s talk a little about its use. Some of these tips might seem like common sense, but that’s not the case for everyone. We know because we weren’t up to speed during our first run, and knowing these might have prevented a few mental breakdowns. 

Take the Time 

Compression tests are easy to perform on a lot of applications. That’s especially true for newer vehicles that have spark plug holes in easily accessible locations. On older models, those holes might be hard to reach due to the lower angle of the plugs and headers that get in your way. Take the time and remove anything that stands in your way. Otherwise, you’ll only be assuming that all cylinders are healthy. 

Quick Connections are Your Friend 

Setting up compression testers can be the one part of the process that keeps you from doing it. Having to thread connections together in tight spaces can be a total nightmare. If you can afford it, invest in a model with quick-connect fittings that will make your life a whole lot easier. 

Mods Change Readings 

On a stock application, you will find the answers you need regarding how much cylinder pressure is typical for your application. However, some modifications throw that reading off. For example, cylinder heads with smaller chambers can increase the number while big cams lower it. It’s important to take these upgrades into consideration while you work. If you’re not sure what your cylinder pressure should be, take a reading of all, and the average highest number should be your baseline to work off of.

FAQs

Compression testers are pretty simple, as is the test you’re performing. That doesn’t mean you won’t have questions, though. That’s why we’re going to answer some of the more popular concerns regarding these tools and this procedure. 

Q: What does a compression test tell you?

A compression test tells us how much pressure the cylinders are building up. This information can be used to indicate the low-rpm performance of the engine as well as the overall health of the cylinders. If reading is low, it means there is something preventing pressure from building up, which can contribute to misfires or poor running conditions. 

Q: Should a compression test be done with the engine hot or cold?

For the most part, a warm engine will provide the most accurate results. That’s because everything has been heated up and expanded to the correct tolerances. However, the test can still be performed cold if you suspect serious damage or other steps prevent you from running the engine before testing. 

Q: Can you check compression without a tester? 

Yes, there are ways to check compression without a tester. An old-school trick is to simply place your finger over the spark plug hole as the engine turns to ensure air is being pushed out. Obviously, this test is inaccurate and can be risky, though. So, it really is best to invest in a compression tester. 

Q: How do you fix low compression?

That depends on the situation, as many different things can cause low compression. For example, faulty rings, leaky valves, and blown gaskets can allow pressure to escape. To determine how to fix it, you must first find the source of your problems. 

Q: Can a compression test hurt your engine?

A compression test can be hard on some parts, but you shouldn’t worry about it harming your engine. It’s a vital diagnostic test that tells you if there are major issues to concern yourself with. Besides, everything will be fine as long as the starter is in good shape and the engine is well-lubricated. 

Final Thoughts

We feel the OTC 5605 Deluxe Compression Tester Kit is a solid choice for the average consumer. It’s accurate, well-equipped, and built well. However, the Betooll W0130 Cylinder Compression Tester Kit is something we think you can count on when cash is tight. What are your thoughts? We’d love to get your input on what compression tester belongs in every garage.

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