If you enjoy working on your car, performing whatever maintenance it needs and fixing any pieces or parts in need of repair, you likely have a wealth of tools and tool kits in your garage. But one of the most important is a diagnostic tool — a compression tester. You have to have a compression tester in order to detect faulty components and make the appropriate repairs. With one of these valuable tools, you can get an accurate reading of your engine’s compression levels. This is key to finding hidden, hard-to-spot engine problems that could lead to damage or loss of function. There are a ton of different compression testers to choose from, all with different fittings, adapters, and other accessories for vehicles and engines of all sizes. If you’re looking for the best of the bunch, check out our picks for the best compression testers right here.
The Best Compression Tester
The deluxe compression tester kit from OTC is the complete package and a reliable tool for car owners and professionals who need a versatile compression device that ticks all the right boxes in terms of durability and accuracy. The adapters work on both tapered and flat seat plugs, and the dual-scale gauge reads 0 to 300 psi and 0 to 2100 kPa. The hose is long enough to position the gauge from where you can see it inside the car.
These features allow you to use the kit to detect bad valves in gasoline engines even if they have cluttered compartments. Moreover, all the components of this kit have a corrosion-resistant finish.
- Large dual scale gauge
- 10 mm, 12 mm and 18 mm threaded connectors
- 12 inches flexible 14 mm connectors
- 16 mm connector for the Ford Triton
- Corrosion resistant nickel-plated finish
- Comes in a molded plastic case
- Brand OTC
- Model 5605
- Weight 4.6 pounds
The pro fuel injection pressure tester kit from BETOOLL is easy to assemble and comes with a dual dial. It is designed to work with any car thanks to the universal pressure gauge and efficient coupler connection. You can easily organize and store the different hoses and adapters inside the red molded case and keep it on a shelf inside your garage or in the trunk for easy access.
- Pressure tester kit for fuel injection systems
- Dual dial for accurate readings
- Efficient coupler connection
- Compatible with most adapters
- Comes in a red molded case for easy storage
- Brand BETOOLL
- Model 5824091208
- Weight 8.55 pounds
The cylinder compression tester kit from 8MILELAKE includes a dual-scale gauge with better air sealing and four different fittings that are compatible with most vehicles. It also includes two versatile adapters with rubber cone ends and a long extension hose. This compression tester allows you to perform carbon buildup inspections in addition to checking the condition of the valves and rings. Everything is neatly packed inside a blue blow mold case.
- Gauge with dual scale with 0-300 PSI, 0-20 kPa
- Includes 14mm and 18mm spark plug adapters
- Straight and angled fittings for use in most vehicles
- 1/2" diameter x 14" extension hose
- Comes in a blue blow mold case for easy storage
- Brand 8MILELAKE
- Model FBA_SZ
- Weight 2.4 pounds
The INNOVA 3612 is popular for several reasons. This compression test kit has a wealth of features, including a dual dial with color-coded scales and an oil-resistant rubber hose with a length of 15 inches. You can easily carry out multiple tests without disconnecting the hose thanks to the side release valve that comes with this kit. There are two different adapters to choose from, and both are compatible with most vehicles. Each set comes with a 12 mm adapter that can be used in snowmobiles and motorcycles.
- Dual calibrated and color-coded dual face
- Long 15-inch rubber hose – oil and grease resistant
- Repeated tests possible thanks to the side release valve
- Durable bourdon tube meter movement
- Includes 12mm and 14mm versatile adapters
- Brand INNOVA
- Model 3612
- Weight 8 ounces
The OTC 5606 is designed for complete compression testing on gasoline engines. Each kit includes adapters that work on both flat and tapered seat plugs and a large dual-scale gauge that reads 0-300 psi and 0-2100 kPa. The 25-inch flex hose can be easily assembled with an efficient coupler, so you can check the condition of the valves without the cluttered compartment getting in the way.
Each component is durable and resistant to corrosion thanks to the nickel-plated finish. The OTC 5606 compression tester kit comes in a heavy-duty case with a removable lid that keeps everything neatly organized and ready for use.
- Dual scale gauge with zero adjust feature
- 12" flex-14 mm standard reach adapter
- 12" flex-14 mm long reach adapter
- 10 mm -12 mm and 18 mm thread adapters
- 25-inch hose for easy viewing
- Corrosion resistant nickel plate finish
- Comes in a blow molded case with removable lid
- Brand OTC
- Model 5606
- Weight 1.72 pounds
The BlueDriver Compression Tester Kit is a high-quality tool set — and it’s designed to be just as suitable for professional mechanics as it is for auto enthusiasts and DIYers. This compression tester kit includes everything you’ll need to take a close look at what’s happening inside your engine.
It has a 2.5-inch triple scale gauge that can measure from 0 to 300 PSI, 0 to 21 kg/cm, and 0 to 20 bar along with a 16-inch rubber hose, 14 millimeter, and 18-millimeter spark plug adapters, a set of four additional adapters, a 45-degree universal direct shaft, and a straight universal direct shaft. And it’s all packaged in a convenient, durable case with a removable storage tray. It’s a comprehensive kit that’ll meet all of your compression testing needs.
- 8 pieces packaged in a tough, organized case
- Two universal direct shafts (one 45 degree, one straight)
- 2.5 inch compression gauge with release valve
- A triple scale gauge with three different options for reading compression
- Brand BlueDriver
- Model BDCT-001
- Weight 2.95 pounds
The Actron CP7828A features a 2.5-inch-diameter gauge with both standard and metric scales. The kit also includes a 17-inch oil and grease-resistant hose with a quick-release connection for efficient use. There are five adapters to choose from, starting with 10mm and ending with an 18mm adapter in addition to a practical repair kit that comes with valves and O-rings.
This handy kit can be used to assess the conditions of piston rings as well as valves and gaskets found in most domestic and imported cars. It can also be used on ATVs, motorcycles and snowmobiles.
- Large 2-1/2-inch dual scale gauge
- Includes 10mm, 12mm, 14mm, 14mm and 18mm adapters
- Side-release valve for repeated testing
- 17-inch-high pressure hose with quick release connection
- Compatible with most domestic and imported vehicles
- Can be used in snowmobiles and ATVs as well as motorcycles
- Brand Actron
- Model CP7828A
- Weight 1.33 pounds
The Orion Motor Tech Compression Tester is a fantastic product to pick if you need a more advanced compression tester. It offers everything you need to quickly test your engine’s compression pressure, and it works on fuel engine cylinders as well as most spark plug types. That means you can put this compression tester to work on your car and other vehicles, like motorcycles, snowmobiles, ATVs, and more. It offers universal compatibility and is very versatile.
All of the components are designed to work on many different engines — it includes multi-sized adapters including straight, curved, and male fittings so you’ll have the tools for a wide array of vehicles. An easy-to-read instrument panel offers readings in PSI and kg/cm. An acrylic glass gauge, which has an anti-scratch coating and protective rubber cover, offer durability. This well-rounded, highly adaptable compression tester can do it all.
- Multi-size adapters to suit a wide range of different vehicles
- Reads 0 to 300 PSI and 0 to 20 kg/cm
- Includes a 14-inch extension hose, spring buckle gauge, straight rubber cone end adapter, curved rubber cone end adapter, and four brass adapters with metric male fittings
- Made with anti-rust materials
- Brand Orion Motor Tech
- Model OMT-MFK2019BU-01
- Weight 2.20 pounds
This compression gauge test set for engine cylinders from PMD Products comes in a blow mold case and has all the necessary attachments for checking valves and piston rings and for inspecting carbon buildup and late timing.
Each set contains a three-inch, dual-color scale gauge with 0-300 PSI. The gauge has a quick push-button release valve and a rubber protector. The set also includes a wide range of adapters that are compatible with most vehicles. The flexible 10.5-inch hoses have schrader valve inserts, and the brass coupler is corrosion resistant.
- Three-inch dual scale gauge with 0-300 PSI, 0-20 kPa
- 10.5-inch reach hoses
- Push-button release valve
- Rubberized gauge protector
- Comes in a red blow molded case
- Brand PMD Products
- Model TU15
- Weight 2.98 pounds
The final test kit on our list is designed for gasoline engines and includes all the necessary attachments required for carrying out both wet and dry compression tests. Pressure readings can be saved on the device, so you can go back and check old readings and save new ones as well. The versatile adapters can be used on motorcycles as well as small and marine engines.
- Digital gauge saves readings for individual cylinders
- Designed for wet and dry compression tests in gasoline engines
- Easy to use adapters can be used on small engines, motorcycles and marine vessels
- Valve seal repairs are possible thanks to the air-hold adapter included in this kit
- Brand Mityvac
- Model MV5532
- Weight 4.65 pounds
Wondering how you can make sure you buy a quality compression tester? There are a lot of options available, and you can find compression testers for every type of vehicle and every type of engine. But in order to buy the right fit for your needs, you’ll want to follow our guide to the best compression testers.
What to Consider When Buying a Compression Tester
Before you can settle on a single compression tester, you’ll want to compare a few top options. And in order to do that, you’ll need to consider what each compression tester offers. The best products will share a few qualities in common —- but you’ll also want to consider how well each option can meet your needs.
Most premium compression testers have more than just the basics and come in a comprehensive kit with several fittings and adapters in addition to other tools that you can use on any engine. This can come in handy if you own more than one car or of you need to check the valves of your motorcycle or all-terrain vehicle. Some models offer extra long hoses that allow you to perform your test and record your readings without the cluttered compartment getting in the way.
Durable compression testers were built to last and most of them have a corrosion resistant nickel finish and a rugged outer boot to protect the gauge and prevent it from breaking. Owning a complete set made of rust resistant components allows you to save money in the long run. Stainless steel sets are also on offer and those have durable hoses and fittings that are ideal for heavy usage and frequent compression testing.
- Accurate Gauge
The gauge should deliver accurate readings either in digital or analog form depending on the model. Knowing how much compression is in the engine allows you to take action and become proactive when it comes to your vehicle. Digital gauges give accurate readings and allow you to save individual results for different cylinders at the touch of a button. This feature makes this type of compression tester more expensive than regular models. Gauges should be easy to read and large enough to hold. Having a dual scale that indicates both metric values and psi is also a bonus.
- User Friendly
Compression testers like the ones listed above are easy to assemble with a user-friendly interface. Large dual scale gauges and detailed instruction manuals make this tool easy to use and incredibly practical. Car owners can use it to check for damaged valves in the comfort of their own garage and without enlisting the services of a professional mechanic.
- Storage Case
Most compression testers come in a special molded case that makes organizing and storing the different fittings and hoses a piece of cake. This case allows you to pack everything you need in case you needed to test your snowmobile in winter or your boat engine in summer. Some cases have detailed instructions on how to use the tester written on the lid itself and this can come in handy if you are a beginner when it comes to compression testing. The case also protects the different components and keeps them in pristine condition.
- Versatile Adapters
Hard to reach spark plugs require a versatile adapter that will make this process a lot smoother and easier to carry out. Therefore, you should look for a functional compression test kit with a wide range of adapters that are compatible with different engines and car models. You also need to make sure that your adapter collection includes options for standard and small sized plugs in case you need to test the engine of a motorcycle or a marine vessel. For example, having a 15-inch-long adapter in your repertoire can make a world of difference when it comes to the compression testing process.
Compression testers are not immune to breakage, especially the gauge since its glass can crack or break if it collides with the hard floors of your garage. The sensitive needle can sometimes malfunction as well , resulting in inaccurate readings. Having comprehensive warranty coverage on your side allows you to get your compression kit fixed without charge.
Why You Should Conduct Engine Compression Test
Conducting engine compression tests allows you to uncover many issues that would otherwise go undetected. Piston rings and engine valves are prone to wear and tear over time and assessing their condition on a regular basis allows you to preserve your precious engine. You can easily perform the test yourself if you have the right kit on hand. Low or zero readings in one cylinder can be caused by several things including a broken valve spring or excessive camshaft wear. If you perform the test on two neighboring cylinders and you end up with low or zero readings, then chances are that you have a blown head gasket on your hands. Low readings can also be a result of a blown head gasket or a damaged camshaft. Excessive carbon buildup can be the culprit behind high readings in one or more cylinders. This buildup can become severe enough to the point where chemically removing it becomes a necessity.
How to Use a Compression Tester Kit
- If your car has a distributor, then you need to pull the wire that leads to the coil from the center of the distributor cap and place the metal connector far away from the spark plugs and against an unpainted metal surface.
- If your ignition system lacks a distributor then you need to disconnect the electrical connecter found in the ignition control module. Consult your neighborhood mechanic if you need help with this step.
- Make sure that the car battery is fully charged before you perform this test. False low compression readings may occur as a result of decreased battery power.
- Different engines require different compression gauges, so make sure you choose the correct model for your car. Diesel engines have different gauge requirements than those fueled by gasoline. The diesel gauge needs to have higher compression tolerance.
- The engine needs to be warmed up beforehand and you can do that by going on a short drive or allowing the engine to idle inside your open garage.
- You will also need to disable the fuel injection system in order to prevent gasoline vapors from escaping through the spark plug holes and becoming a fire hazard.
- Remove the fuel pump fuse before starting the car. Allow it to run until it runs out of gasoline and stalls as a result.
- Each spark plug is connected to a wire via an ignition boot. Remove each boot and label it properly. Labeling prevents you from getting the wires mixed up and damaging your engine in the process.
- Place all the removed spark plugs on top of a clean and dry surface. Line them up in order of removal in order to return each one to its respective cylinder later.
- Switch to the battery once you connect the starter.
- Connect your remote starter switch to the battery’s positive terminal and to the starter solenoid terminal as well.
- Connect the compression gauge but make sure to insert it where the first spark plug used to be.
- Use the remote starter switch to crank the engine around 6 times. This step always requires the gauge plug to be firmly inserted .
- Record the reading that appears in the gauge before hitting the reset button.
- Repeat the above steps for the other cylinders as well. Make sure that you crank the engine and hit the reset button for each cylinder you test.
- Check all your recorded readings once you finish conducting this test.
- Return each spark plug to its original cylinder and make sure that you turn off the engine before reconnecting the wires.
- You can also perform a wet test while the spark plugs are still removed. All you need to do is add around one teaspoon of motor oil into the spark plug hole before taking another compression reading and comparing the difference between the wet and dry tests. Oil is used during the wet test since it offers a wet seal for the rings. Issues with the piston rings or cylinder walls are identified if the compression increases with the wet test. If the compression value does not change then something could be wrong with the valve train.
Best Compression Tester FAQ:
Q: What is a Compression Tester?
A: A compression tester is a basic tool with a pressure gauge and other removable components that allow you to insert it into a spark plug hole or diesel injector socket. This tool was designed to measure engine pressure and provide accurate data that is presented in pounds per square inch or PSI. Compression in a vehicle is incredibly important when it comes to both diesel and gasoline engines, which is why performing this compression test can help you assess the condition of several engine parts including the valves and piston rings. All you need to do is disconnect the ignition and fuel systems before cranking the engine several times. This procedure is applied to each cylinder and the resulting readings are then compared to each other. A healthy engine has a compression of more than 100 PSI in each cylinder. Wear and tear cause the engine to lose compression over time but compression levels of around 180 to 220 PSI fall within the acceptable limit. A compression less than 85 psi may indicate a serious problem with the engine. Higher compression is required by diesel engines due to the massive pressure needed to ignite the diesel. These engines have a compression of around 350 PSI.
Q: How Does Engine Compression Tester Work?
A: Engine compression testers measure cylinder compression and most of them are sold in a complete set with universal adapters for standard and small spark plug threads. Each compression tester comes with a hose that you need to screw into the spark plug hole that belongs to each individual cylinder. The gauge is then hooked up to the other end of the hose. Once you begin cranking the engine, the needle inside the gauge will climb upwards along the scale until it reaches a certain point where it stops moving. You need to test each cylinder and write down each reading for comparison. All readings should be similar with no more than 10 to 15% variance across all cylinders.
Another version of this test is called a leakdown test and this one uses a more elaborate tool that hooks up to an air compressor. Air is pumped into the cylinder while the valves are closed, allowing the mechanic to check for leaks. Piston ring issues result in air hissing out of the dipstick tube or crankcase above the engine. Valve issues cause hissing sounds from the intake or exhaust and bubbles rising from the coolant could mean that the cylinder head is damaged or fractured, or that the headgasket is broken.
Q: How Should I Care of My Tester?
A: Sometimes, a grain of sand or even a small particle of carbon can cause the gauge needle to malfunction. A dirty compression gauge can result in inaccurate readings; therefore, you need to wipe any oil or grease that may have made its way to the surface of the gauge and its attachments. This tool is designed to deliver accurate readings, so you need to store it somewhere dry and cool and as far away from heat and moisture as possible. Make sure to return all the attachments to their respective place inside the blow molded case. The cleanliness of the spark plugs also matters, and you can easily remove the dirt and grime that may have settled on these components with the help of compressed air.
Our Top Pick
If you’re looking for the best compression tester available, you’re going to want to consider the OTC 5605 Deluxe Compression Tester Kit. It’s our top pick because it offers a wide range of different features and capabilities, yet it remains easy to use and easy to understand. This compressor tester is a complete set of attachments for every one of your possible needs, all packaged in a convenient and tough heavy-duty molded plastic case. When you use this compression tester, the dual scale analog dial gauge will deliver accurate readings in both PSI and metric measurements. You’ll be ready to conduct tests with threaded flexible connectors, a wide selection of different attachments in different diameters, and more. Every item in this kit is even made with corrosion-resistant nickel-plated finish, which offers an extra level of durability to ensure you can keep using this tool for a long time to come.