Best Engine Flush: Keep Your Motor Running Strong

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

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Just as your heart cannot function properly when your arteries are blocked, the engine in your vehicle runs poorly when it’s clogged up with dirt and deposits. Engine flushes help clean this sludge so your engine can run smoothly and last longer. So what is the best engine oil flush available? Read on to see our top picks.

  • Best Overall
    Liqui Moly 2037 Pro-Line Engine Flush
    The best motor flush is quick, easy, and effective at clearing out sludge in your engine.
    Protects against corrosion, compatible with both gas and diesel four-stroke engines, improves oil circulation, neutral to seals and gaskets.
    Doesn’t cut down on oil consumption.
  • Best Value
    Sea Foam Marine and RV SF-16 Engine Flush
    The best engine cleaner flush for drivers on a tight budget.
    Targets the parts of the engine most affected by fuel deposits, EPA-registered, affordable price tag.
    Inconsistent results with some higher mileage vehicles, the package is difficult to open.
  • Honorable Mention
    Lubegard 95030 Engine Flush
    This Lubegard engine flush delivers on its promise to remove sludge, varnish, and by-products left behind from combustion.
    Easy to use, compatible with gas and diesel four-stroke engines, premium synthetic blend, safe on gaskets and seals.
    Slightly expensive.

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


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.

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.


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.


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.


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, antiwear 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 2019

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

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 by-products 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.

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

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. 

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Best Engine Flush Honorable Mention: Lubegard 95030 Engine Flush

Lubegard 95030 Engine Flush

The Lubegard 95030 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 95030 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.

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  • 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.


Q: What is an engine flush?

A: 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?

A: One of the most common causes of carbon build-up 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?

A: 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?

A: 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?

A: 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

The Liqui Moly 2037 Pro-Line Engine Flush is the best engine flush cleaner overall because it’s a quick and easy way to thoroughly rid your engine of performance-sapping sludge and deposits while extending longevity.

A more affordable motor oil flush is the Sea Foam Marine and RV SF-16 Engine Flush.

Have you flushed your engine with any of these products? Do you have another preferred brand? Voice your opinion in the comments below.