Reviews

Best Engine Flush: Keep Your Motor Running Strong

An engine flush is an affordable way to maximize your engine health.

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BY Noelle Talmon / LAST UPDATED ON May 11, 2021

After a while, your engine may start accumulating sludge and deposits that can adversely affect your vehicle's power and performance. These contaminants can clog oil passages, restrict oil flow, cause rings to stick, and generally reduce compression and horsepower. If you want to eliminate this unwanted gunk, you can use an aftermarket engine flush. 

Simply pour it into the oil filler so it will circulate through the engine and remove deposits. Then you drain the oil, which should be full of the harmful deposits, swap out the oil filter, and add new oil. Many types of engine flush products are available online and in stores, so it can be tough to choose the best one. Check out some of the best options in the buying guide below.

Best Overall
Liqui Moly 2037 Pro-Line Engine Flush
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Summary
Summary

The best motor flush is quick, easy, and effective at clearing out sludge in your engine.

Pros
Pros
  • Protects against corrosion, compatible with both gas and diesel four-stroke engines 
  • Improves oil circulation
  • Neutral to seals and gaskets
Cons
Cons
  • Doesn’t cut down on oil consumption
Best Overall
Liqui Moly 2037 Pro-Line Engine Flush
Best Value
Sea Foam Marine and RV SF-16 Engine Flush
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Summary
Summary

The best engine cleaner flush for drivers on a tight budget.

Pros
Pros
  • Targets the parts of the engine most affected by fuel deposits
  • EPA-registered 
  • Affordable price tag.
Cons
Cons
  • Inconsistent results with some higher mileage vehicles 
  • Package is difficult to open
Best Value
Sea Foam Marine and RV SF-16 Engine Flush
Honorable Mention
Lubegard 95030 Engine Flush
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Summary
Summary

This Lubegard engine flush delivers on its promise to remove sludge, varnish, and by-products left behind from combustion

Pros
Pros
  • Easy to use
  • Compatible with gas and diesel four-stroke engines 
  • Premium synthetic blend 
  • Safe on gaskets and seals.
Cons
Cons
  • Slightly expensive
Honorable Mention
Lubegard 95030 Engine Flush

Why Trust Us


All of our reviews are based on market research, expert input, or practical experience with most products we include. This way, we offer genuine, accurate guides to help you find the best picks.

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Benefits of Engine Flushes

  • Remove sludge, deposits, and dirt. Over time, sludge, carbon deposits, and gunk can accumulate in your engine, increasing wear and reducing power as well as fuel economy. Using an engine flush in your vehicle helps remove these performance-draining dirt and deposits.  
  • Clean hard-to-access engine parts. Unfortunately, you simply cannot access most engine components without completely tearing it apart. The best engine flush products will clean out vital engine components without the need to perform open-engine surgery.
  • Keep your new motor oil cleaner. Putting clean oil into a dirty engine means your new oil won’t stay clean for very long. A high-quality engine flush will ensure that no harmful deposits and sludge are left behind when you change the oil so your new oil can lubricate vital engine parts as effectively as possible.
  • Improve your fuel economy. Contaminants circulating throughout your engine can result in oil breakdown and increased viscosity. Additionally, sludge and deposits on engine parts can increase resistance, which wastes fuel. Cleaning your engine with an engine cleaner flush helps parts move more efficiently, maximizing your fuel economy.
  • Help minimize emissions. If carbon deposits in the piston-ring cause the rings to stick, oil can find its way into the combustion chamber and burn. This results in harmful deposits and increases exhaust emissions as the burned oil exits the tailpipe. The best oil flush treatment helps free stuck rings and minimize oil consumption, in effect lowering your emissions.

Types of Engine Flushes

Gasoline Engine Flush

This type of engine flush is specially formulated to work in vehicles powered by gasoline engines. There are gasoline engine flush products made for particular applications such as higher-mileage engines, as well as some designed to work as quickly as possible. The best oil flush products for gasoline engines will utilize a proprietary blend of additives to rid your engine of harmful deposits and sludge.

Diesel Engine Flush

If your car, truck, or SUV is powered by a diesel engine, you’ll want to only use a diesel engine flush. This type of engine flush is specifically engineered to flush out the harmful carbon deposits, gunk, and sludge that build up in diesel engines over time. A common subcategory of diesel engine flush products is diesel truck or SUV flushes. 

Gasoline & Diesel Engine Flush

The other common type of engine flush you’ll find on the market today is a flush formulated to work effectively in both gasoline- and diesel-powered engines. These versatile engine flush products are convenient because they can be applied to either engine type so you don’t have to worry about buying an engine flush specifically made for a gas or diesel engine.

Top Brands

Liqui Moly

Established in 1957, Liqui Moly is a German company that makes oils, lubricants, and additives for automobiles. Liqui Moly positions itself as offering premium-quality products at a more affordable price point than its competitors. One of its most popular products is the Liqui Moly 2037 Pro-Line Engine Flush.

Sea Foam

Dating back to the 1930s, Fred Fandrei, a salesman in the petroleum industry, created a fuel additive for his boat in hopes of making the motor run better. His creation became wildly popular with his fishing buddies and eventually became one of the most trusted engine flush products for boats and motor vehicles. One of its best-selling products is the Sea Foam Marine and RV SF-16 Engine Flush

STP

Introduced in 1953, Scientifically Treated Petroleum (STP) is an American brand and trade name for automotive aftermarket products. STP is widely known for manufacturing lubricants such as engine oil and additives like engine cleaner flush. One particularly popular product is the STP Ultra 5-in-1 Fuel System Cleaner.

LUBEGARD 

LUBEGARD is a brand of International Lubricants, Inc. (ILI), based in Seville, Ohio. Its products are popular among professionals in the automotive service industry due to their excellent performance. Check out the Lubegard Engine Flush.

Motor Medic

Motor Medic makes products for the following systems: brake, cooling, diesel, fuel, oil, power steering, and transmission. The company has been in business for decades and aims to help customers maximize their vehicles' performance while keeping maintenance costs down. We recommend the Motor Medic Synthetic Motor Flush.

CRC

CRC has been producing products for maintenance and repair needs in a variety of industries, including automotive, marine, heavy truck, and aviation, since 1958. It's part of the CRC Industries Americas Group, which is based in Horsham, Pennsylvania. Check out the CRC Salt Terminator Engine Flush.

Hapco

Hapco, based in Michigan, has been making a range of automotive products since 1960. The founder made his first product, a vinyl and upholstery cleaner, in his kitchen. Today, you can purchase carburetor cleaners, cooling system sealers, fuel injector cleaners, and other products from the company. We like the Hapco Fast Motor Flush.

Engine Flush Pricing

  • Under $10: Shoppers will find a few value-priced options for under $10. These affordable products offer decent performance for a modest price and remain popular largely due to their excellent value.
  • $10 - $19: Consumers will delight in the vast amount of engine flushes available in this price range. The majority of motor flush products at this price point are simple to use and deliver excellent sludge-busting performance.
  • Over $19: There are just a select number of options priced above $19. Shoppers will find some of the best oil flush products around this price point, though some of the more affordable options may be just as effective but lack the brand cachet of these pricier offerings.

Key Features

Engine Type Compatibility

The most critical feature of engine flush products is engine type compatibility. Motor flushes can be compatible with gasoline or diesel engines, and in some cases, both engine types. For best results, it’s important to only use an engine flush formulated for the type of engine in your vehicle. Many consumers elect to use an engine flush treatment designed for both gasoline and diesel engines because they don’t have to worry about engine compatibility.

Solvents

Many engine oil flush products use a formula that contains solvents to assist with cleaning any carbon deposits, gunk, and sludge that accumulate in your engine. While mild solvents may be handy in clearing out sludge in high-mileage engines, most consumers will want to avoid purchasing an engine flush that contains too many solvents because they can deteriorate engine seals and gaskets.

User-Friendliness

Another prominent feature of engine flushes is the user-friendliness of the product. The majority of engine oil flushes are designed to be easy to use without the aid of an engine flush machine, but a few require the use of special tools that attach to a garden hose to flush out your engine. You’ll want to consider your mechanical skill level as well as any time constraints before selecting the right product for your needs.

Additives

An engine flush is essentially a blend of specific additives mixed into a single solution. With that said, different engine flush products contain different additive blends which are frequently engineered to deliver a specific result. The best engine flush product generally contains a mix of detergents, dispersants, anti-wear additives, lubricants, and rust inhibitors. Make sure the engine flush you’re interested in contains at least a few of these additives for maximum cleaning power.

Other Considerations

  • Quick Results. If time is a major factor for you when it comes to flushing your engine (and when is it not important?), you’ll want to consider an engine flush that is designed to deliver quick results. Many popular brands boast that their product works in as little as 10-15 minutes, saving you tons of time without sacrificing satisfactory results. 

Best Engine Flush Reviews & Recommendations 2021

Best Overall
Liqui Moly 2037 Pro-Line Engine Flush

The Liqui Moly 2037 Pro-Line is the best engine flush cleaner in our comparison because it’s refreshingly easy to use and safely removes harmful deposits, debris, and byproducts of combustion in a brief amount of time. 


Liqui Moly proves that flushing your engine doesn’t have to be a headache—simply pour the 2037 Pro-Line engine flush into your warm engine and let it idle for about 15 minutes. Then drain the old oil, replace the filter, and refill with new motor oil. The specialized formula contains additives designed to safely eliminate all forms of dirt, grime, varnishes, and gums that accumulate in your engine. For added versatility, this product is formulated to be equally effective as a diesel engine flush as it is a gasoline engine flush. 


Our only gripe is that this flush doesn’t reduce oil consumption, so you may want to consider another option if your ride chugs oil in between changes. Nonetheless, the Liqui Moly 2037 Pro-Line engine flush is the best engine sludge cleaner for most engines.

Best Value
Sea Foam Marine and RV SF-16 Engine Flush

For drivers looking for a more focused approach to engine flushing, the Sea Foam engine flush certainly offers a compelling formula designed to target specific parts of your engine as opposed to a more general complete flush. This engine flush specifically targets carb jets, injectors, and passageways. 


The flush also focuses on pistons, intake valves, and cylinders. If your engine is equipped with these components, this motor oil flush targets the VVT actuators and timing chain tensioners to ensure everything is thoroughly cleaned. Next, it meticulously dissolves any oil residue found in the crankcase. Finally, this Sea Foam-flush then goes to work cleaning your fuel system to make sure no fuel residue still lingers.


The systematic approach restores engine performance and efficiency, but it’s not always noticeable. There are some reports of people with higher-mileage cars not noticing any improvements in engine response or efficiency after using Sea Foam. Additionally, some of the packages can be tricky to open, so make sure you follow the instructions carefully when opening the bottle. 

Honorable Mention
Lubegard Engine Flush

The Lubegard engine flush promises exceptional engine cleaning power, user-friendliness, and virtually universal compatibility, but falls short of the best engine flush additive in our guide due to its high price.


The majority of premium synthetic oil contains detergents and dispersants which prevent tiny particles from sticking to the surface of your engine and its passageways. But they’re not as effective when your engine is full of contaminants. The synthetic blend in Lubegard cleanses your engine and optimizes the efficiency of your engine oil to make your vehicle run at its best.


This engine flush is also extremely easy to use, working its magic on removing sludge and deposits from your entire engine in just 15 minutes or less. Another benefit of the Lubegard engine flush is that owners of vehicles with gasoline or diesel four-stroke engines will enjoy the same superior sludge-cleaning performance. And despite its potent cleaning properties, this engine cleaner flush is easy on your engine’s seals and gaskets. 


Drawbacks are few and far between, but if we had to focus on one, then it would be the high price tag that this engine flush commands. The Lubegard is more expensive than most of its competition. Noticeable improvements may also be lacking after you have applied the flush into the engine.

Honorable Mention
STP 18566 High Mileage Engine Flush

STP 18566 provides a concentrated deep clean for engines with more than 75,000 miles. It dissolves the carbon deposits that can build up in your engine’s intake valves and combustion chamber, and clears away sludge buildup on your cylinder heads, stretching out the effectiveness of your next oil change.


STP’s engine flush makes our favorites list because of how easy it is to use, and how quickly you’ll see results. Application is as simple as pouring it through a heated-up engine. What’s more, is you’ll notice your engine running quieter almost immediately. This is a great option for drivers who’ve been having problems with engine noise, as it cuts down on ticks and knocking in higher-mileage vehicles (so long as they aren’t being caused by some deeper problem).


There’s hardly anything we don’t like about STP 18566, but if there are any drawbacks, it’s that you don’t get many uses out of one bottle. It’s also important to be aware of the potential consequences of using any solvent in your engine, as flushes can sometimes fail to completely remove deposits, leaving them in the engine to cause more damage.

Honorable Mention
Bg109 Engine Performance Restoration

Bg109 is a rigorously tested engine performance enhancer that we like a lot for both brand new and high-mileage vehicles. It’s great for cleaning out engine deposits and reversing drops in fuel efficiency. While the can warns users not to apply it to engines with “excessive sludge,” this is a fairly high bar—we’ve found that Bg109 works well at many different levels of engine cleanliness.


Using it requires 15 minutes of running your engine before getting an oil change. Tests run on Bg109 prove that it’s effective at increasing compression, both that of individual pistons and of the engine as a whole. If you’ve noticed your car burning oil too quickly, flushing it with Bg109 can also help with that problem, allowing you to get much more efficiency out of each oil change.


The drawback of Bg109 is that it doesn’t do much that regular maintenance won’t. It’s only useful as a corrective if you’ve missed too many oil changes, or have deposits resulting from another underlying problem. The cans are also quite small, too, requiring you to buy two if your engine has a 7-quart crankcase (and they aren’t cheap).

Honorable Mention
Resurs Total Engine

Resurs makes a cheap, effective engine flush that works on any gasoline or diesel engine. While simple to use—it only requires an extra 10-15 minutes on top of the time an oil change takes—it packs a punch, sometimes burning out enough carbon deposits to reduce oil burning by 80 percent.


We were intrigued by Resurs Total Engine after seeing how successful it’s been in both Russia and the United States, and it really impressed us with its ability to cut down on noise and extend an engine’s life. It can even make engines more environmentally friendly by reducing the volume of smog they put out. A single can is pretty affordable, and the price includes detailed instructions, in case you’ve never performed an engine flush before.


Is there anything holding us back from giving Resurs Total Engine the top spot? One drawback concerns volume versus price. While one can is cheap, it’s also likely to not be enough. It’s also less effective for use in older cars.

Honorable Mention
Motor Medic Synthetic Motor Flush

The Motor Medic Motor Flush requires just five minutes to take effect. It removes sludge, gums, varnishes, and other deposits and contaminants in your engine. It lets oil circulate better, releases sticky valves and piston rings, restores performance, and prolongs an engine's lifespan.


This product is designed to be used before each oil change. It minimizes oil consumption, corrects noisy valves, and promotes a smoother-running motor. Motor Medic's formula won't damage seals or wear down bearings, and it works with gas, non-turbo, turbo, and diesel engines. Users report that it works well as long as you follow the directions. It's a great option if you purchase an older vehicle and are unsure of its maintenance history, and overall it does what it advertises.


There are not many complaints about this product, except that the formula looks and smells a little like kerosene, which may be off-putting. There have also been some complaints that you may need to remove the oil pan before using it.

Honorable Mention
CRC Salt Terminator Engine Flush

The CRC Salt Terminator Engine Flush is designed to flush marine engines, but it can also be used for trailers, automobiles, RVs, motorcycles, ATVs, and other vehicles that are exposed to saltwater, salt air, and road salt. The formula is designed to dissolve salt and create a protective coating that prevents corrosion.


The Salt Terminator is biodegradable and is available in a one-gallon concentrated formula. You can use it to service outboards, I/Os, and personal watercrafts. It is water-based and safe to use with plastics. Users report that it does an excellent job of getting rid of salt and is easy to use—simply dilute it according to the instructions, spray it on, brush it on the surface area, and rinse it off. You can also flush saltwater out of the engine.


However, you may have to apply it more than once to remove the salt effectively. Some users report that it's not quite as strong as Salt Away, another popular salt remover, corrosion inhibitor, and motor flush

Honorable Mention
Hapco Fast Motor Flush

The Hapco Fast Motor Flush efficiently and easily cleans vehicle engines. It removes moisture, gum, sludge, varnish, and carbon deposits from the engine's upper cylinder areas, oil lines, pump screens, and piston rings. This product is designed to prevent oil consumption, overheating, and hydraulic lifter noise.


Fast Motor Flush also improves performance and minimizes engine wear: simply add a bottle to the oil reservoir before you change the oil. Run the engine for 15 minutes, and then change the oil. It's designed to be used with every oil change to increase gas mileage and prolong engine life. Users report that it does a good job of removing sludge.


The biggest downside with this product is that it's a little pricier than some other options, but if you're willing to spend a little more, it'll do the job.

Honorable Mention
ATOMEX Total Flush

The ATOMEX Total Flush is compatible with all engine types, including automobiles, motorboats, and motorcycles, and is safe to use with all engine oils and turbocharged engines. It cleans and protects the engine oil system and prevents residue from building up. The formula removes carbon and restores the mobility of oil scraper and compression rings.


ATOMEX cleans the crankcase ventilation system, ensures that the oil system is free from contaminants, and provides anti-wear protection properties. In addition, it minimizes possible defects on friction surfaces. Users report that their engines run smoother and are a little quieter after using this product. It's also a good option for older vehicles and removes debris from your system. It's also easy to use when you're changing the oil.


However, there have been some complaints that the product causes engines to seize. Make sure you read the specs to ensure it's intended for your particular vehicle.

Tips

  • Always change your motor oil frequently using premium-quality synthetic oil whenever possible. This can help stave off the accumulation of carbon deposits, sludge, and grime in your vehicle’s engine.
  • Avoid taking frequent short trips around the city. Brief stop-and-go driving like this can result in the build-up of harmful deposits and sludge in your engine, sapping both performance and fuel economy.
  • Do not buy engine flushes that contain harsh chemical solvents. These solvents can wear down your seals and gaskets, which can cause a variety of mechanical issues. Engine flush products formulated with mild solvents can sometimes be helpful for stuck lifters or rings in older engines. 
  • Always use engine flushes right before you’re about to change the oil. This ensures that all the accumulated carbon deposits, sludge, and other gunk in your engine are flushed out along with your oil. 
  • Remember to carefully read the engine flush bottle to learn important information such as oil-grade compatibility and expiration dates. Always follow the manufacturer’s instructions when performing an engine flush on your vehicle.

FAQs

Q: What is an engine flush?

An engine flush is an aftermarket additive engineered to flush accumulated deposits, sludge, and other gunk out of your engine. You simply pour it into your engine’s oil-filler port and let your engine idle for roughly 10-15 minutes. It blends with the oil and circulates through your engine, dissolving sludge. Next, you drain the oil, change the oil filter, and add fresh oil.

Q: How do I know if my engine needs to be flushed?

One of the most common causes of carbon buildup in your engine is taking frequent short trips. If you notice your ride doesn’t feel as peppy as it usually does or if there’s a drop in fuel mileage, you may need to flush your engine. Other signs include a premature oil change light, signs of oil splatter or sludge under your hood, and sludge present in your oil pan.

Q: What is the best way to flush engine oil?

Engine flush machines are great for speeding up engine flushes; however, they can be very expensive. Most drivers elect to do the job without the assistance of an engine flush machine. If you know how to change your own oil, then you possess the mechanical skills necessary to perform an engine flush job on your vehicle. 

Q: How long does it take to flush my engine without a machine?

The exact time it takes to flush your engine without the aid of a machine depends on the motor flush you’re using. The best engine sludge cleaners take as little as 10 to 15 minutes for a person of modest mechanical capabilities to perform. If you’re new to the whole wrenching thing, then the whole process will obviously take slightly longer.

Q: How much is an engine flush?

Most engine flushes cost anywhere from $7 to $19 for a 15- or 16-ounce bottle. You’ll want to also factor in the cost of a replacement oil filter and motor oil. Most people choose to flush their engines without the aid of a professional, but if you do choose to have a mechanic perform the job, expect to pay anywhere from $100 to $150 in parts and labor. 

Final Thoughts

Our pick for the best engine flush is the Liqui Moly 2037 Pro-Line Engine Flush. Not only is this formula quick and easy to use, but it prolongs an engine’s lifespan by effectively removing sludge and other deposits. 

For a more budget-friendly option, consider the Sea Foam Marine and RV SF-16 Engine Flush.