Best Engine Flush of 2021 – Best Engine Cleaner Reviews

Everyone who has even the slightest experience with cars knows that the engine is what keeps the vehicle alive. Being such an important cog in this complex machinery it is expected that an engine sustains a lot of attrition and wear and tear while they are working.

One of the best ways to help them sustain such pressure and extend their lifespan is to keep them clean and well-maintained. So far the easiest way to do that is to fill the engine with an appropriate cleaner and flush out all the existing particle deposits.

But what is the best engine flush you can currently find in the stores? Let us try to find that out together.

In a Hurry? The Winner after 32 Hours of Research:

Liqui Moly 2037 Pro-Line Engine Flush

Our Rating: 95/100

Why it is the best?

  • Incredibly easy to use
  • Works on both major types of engines
  • Excellent cleaning performance
  • Good priming for an engine oil change
  • Boosts engine performance
  • Not overly expensive
  • Amazon bestseller
  • Great customer feedback

How I Picked:

16 Resources 

188 Reviews Compared

32 Hours Of Research 

24 Popular Products Considered

Last Updated: June 09, 2021

By James Ruhle: This article has been updated to reflect the most accurate information regarding best engine flush available for those who are interested in enhancing their engine. The best 5 available have changed, and information has been added to assist individuals in finding the best engine flushers currently available on the market. The FAQ has also been updated.

Current Top Fuel Stabilizers On The Market- Comparison Table


Type Of Engine

Package Size

Our Rating

Current Price

Liqui Moly 2037 Pro-Line Engine Flush

Gas and diesel

17 Ounces


Lubegard 95030 Engine Flush, 15 oz.

Gas and diesel

15 Ounces


Prolong Super Lubricants PSL11000 Engine Treatment - 12 oz. , White

Gas and diesel

12 Ounces


Golden Touch 1698 Fast Flush Engine Flush - 128 fl. oz.

Gas Only

128 Ounces


Energy Release P023 Motor Flush - 15 fl. oz.

Gas and diesel

15 Ounces


Sea Foam SF-16 Motor Treatment - 16 oz. , white

Gas and diesel

16 Ounces


High Milage Engine Flush Formula, Oil Cleaner for Cars and Truck, 15 Oz, STP

Gas Only

15 Ounces


Niteo Motor Medic MF3 5-Minute Motor Flush - 32 oz, Multicolor

Gas and diesel

32 Ounces


Best Engine Flush Buyers Guide

The grades above were the overall impressions of the products I am going to discuss in greater depth further down below. But, what criteria I used to rank them? Or even better, what makes a good engine cleaner in the first place?

These things are hard to answer. You see, the engine flushes I prefer may not necessarily suit your vehicle and fit your budget. That is why I comprised this short buying guide that will help you find your ideal pick in case you don't agree with my choices.

Here a couple of things to take into consideration before buying an engine flush.

The type of engine flush additives

To keep the things simple, various engine flushes feature different additive formulas designed to address different engine problems. Sure, their overall goal is engine flushing and prevention of particle buildup but, based on the additives that are used, you may get drastically different performance.

The additives themselves can be divided into five major groups:

  • Detergents - This additive is the major ingredient responsible for dissolving accumulated motor sludge. Usually, they are based on alcohol and acids.
  • Dispersants - Essentially, the role of dispersants is to break up solidified carbon deposits. They are necessary for cleaning hard-to-reach areas like the power system.
  • Antiwear - One of the most common non-essential additives. What antiwear does is to use some type of metal to bond the materials in the engine and prevent future wear and tear. If you are looking to get this type of remedy keep in mind that these agents work best when combined with harsh detergents.
  • Lubricants - The main purpose of the lubricants is to reinforce new oil used after the engine is flushed, thus extending the mileage of the oil.
  • Rust inhibitors - This additive is not as common as previous mentions but you can find it a lot of famous products out there. As you can guess its primary purpose is to prevent corrosion of the material. But due to their specific formula, they work well only when put in milder engine flushes.

Depending on the state of your vehicle's engine, you should choose the product that features one or several of these important ingredients.

Type of the engine flush

In this case, the rules are very simple. In other words, the engine flushes, in broad strokes, are dived by the type of the engine they are designed to service. Still, here is a short breakdown:

  • Gasoline engine flush - So, you get the idea of which type of vehicles you should use this group. You should, however, know that some of the products in this category are designed for fast-reacting time or vehicles with high mileage.
  • Diesel engine flush - Due to the specific nature of this type of motor (and fuel for that matter). the diesel engine flushes are usually engineered to double down on removing the gunk that builds up inside the unit. In other words, they are harsh and potent.
  • Gasoline and diesel engine flushes - These products are all about convenience. However, the novelty of not having to worry about the engine type often comes at the cost of convenience.

Ease of use

The majority of engine flushes currently available on the market do not require any special skills or equipment to be used. However, some specialized products require special tools you need to attach to a garden hose before application. The fair knowledge of mechanics is also highly advised. Consider your available time and mechanical proficiency before picking one of these products.


This consideration is incredibly important. Essentially, there are a lot of different engine flush formulas that don't work well with certain types of engines. One of the best examples of this are the modern car engines that contain non-standard materials susceptible to damage by some of the harsher ingredients like, for instance, acid. So, do your best to consult the owners manual before spending money on any of these products.

Of course, we could count the price of the package, size of the bottle, and similar things as important considerations as well. But, all these things are more concerned with your maintenance habits so I won't elaborate too much on them. You get the idea.

Best Engine Flush Products On The Market- Individual Reviews

Liqui Moly 2037 Pro-Line Engine Flush

Our Rating: 95/100

When it comes to popular engine flushes, Liqui Moly comes as close to perfection as it gets. After the extended testing of this package I can say that 2037 Pro-Line flush lives up to the expectations I have from this famous brand and easily makes one of the best entries on the list.

So, what makes this engine flush so special?

Well, first of all, the product is incredibly easy to use. The only thing you need to know is to remove the motor oil cap and you are good to go. After that keep the car turned on for about 15 minutes, remove the flush cap and that's it. So, write in a couple of points in the convenience section.

The second thing I like is that the formula can be used both on gasoline and diesel engines. But, this versatility doesn't come at the cost of efficiency. On the contrary, although the additives used in the mix are very gentle they are productive, so I didn't have any problem removing all sorts of greases and sludge in the vehicles I used for testing.

At the same time, the flush was tame enough to leave the various non-metallic parts like seals entirely undamaged. Believe me, formulas that are as balanced as this one are not that easy to find.

What did I get after I flushed the engine and performed oil change?

First and foremost, I would like to mention the evident changes in oil consumption and fuel economy. The vehicles were running smoother and produced less noise. The second thing I experienced was less struggling when driving uphill. Overall, I am more than pleased with the results.

Are there any drawbacks? Sure, but in this case, they are not truly deal-breakers.

For instance, although the formula of additives in this product is extremely well-mixed, the flush doesn't really perform great in case of old, worn-out engines where grime solidified and now blocks some parts of the engine. Trying to break down these deposits with this bottle will earn you a one-way ticket to the mechanic.

Also, we can't escape the feeling that, in spite of great performance, the bottle is still too pricey for a wast majority of car owners. If you can live with these two things, give it a try - you won't regret it.


  • Efficient and versatile performance
  • Very easy to use
  • Improves engine performance
  • Neutral to sensitive parts


  • Not suitable for older engines

Lubegard 95030 Engine Flush, 15 oz.

Our Rating: 90/100

Lubeguard is yet another famous brand on this list so you can only guess just how excited we were to test their latest motor flush. Much like in the case of Liqui Moly 2037 Pro-Line Engine Flush very pleased with the overall results. Unfortunately, not as pleased. The difference was marginal but we were still able to take notice.

But, let's not get ahead of ourselves.

Lubegard 95030 Engine Flush is yet another product designed to be used both on gas and diesel engines. That gives you a pretty good idea about its mix of additives - the formula is strong enough to break down most of the gums, varnishes, engine sludge, and other harmful deposits but not strong enough to damage seals and gaskets.

And once again, the flush is extremely easy to use. The only thing you need to do before you drain the oil is to pour down the liquid into the engine and keep the car running for a couple of minutes. Although the manufacturer claims you can get away with 5-10, we advise that you go with standard 15 minutes treatment for the best possible results.

And what can we say about results?

Well, they are great. We can say it boarders exceptional. But the engine performance you get after engine flushing falls just an inch behind we got with Liqui Moly. Your car will run smoother and make less noise, but the changes in fuel economy are not that visible. The same can be said about oil consumption.

So, this product is definitely oriented more towards proper maintenance rather than optimizing engine performance.

As for actual drawbacks they are few and far in between but there are still a couple of things worth talking about. Much like its direct competitor features a somewhat hefty price tag that is, in this case, even less warranted. And then there is the same old issue with older engines that don't really blend well with the multi-type products like this.

Use it at your own responsibility.

So, we can't resist but to recommend this product. You won't be disappointed as long as you don't expect noticeable engine performance improvement. As far as cleaning and maintenance go - it's great.


  • Great cleaning properties
  • Very user-friendly
  • Removes sludge and deposits


  • Doesn't improve car performance
  • Slightly expensive

Prolong Super Lubricants PSL11000 Engine Treatment - 12 oz. , White

Our Rating: 95/100

If you take a look at the Amazon rating of this product you will see that Prolong Super's engine flush is very highly regarded amongst the customers. If you take a look at its price you will see that these are only the selected few. Of course, the price of this package is not that off the charts, but why would you pay more for the same performance you get with similar, more affordable products.

So, once again we have a formula that was engineered to work with metallic surfaces of gas and diesel engines. According to the manufacturer, the product features a specially devised formula that doubles-down on anti-friction properties and helps molecules to bond and create a new protective layer on the parts within the engine.

So, if you are looking for antiwear properties, this bottle is definitely for you.

The engine flush is also extremely easy to use. Follow the procedure we have described in the FAQ section and you will be able to perform oil change and engine flush without breaking a single sweat.

In terms of overall results, our impressions are split. Although we haven't noticed any breakthrough improvements in terms of fuel economy with newer vehicles, the changes were more than noticeable when we tried using engine flush on older cars, you could see improvements in almost all areas.

Namely, the oil consumption on tested vehicles became drastically lower. We also felt the cars were running more smoothly on all types of terrain and finally, the rattle on the startup was as good as gone. And we are talking about a couple of vehicles we used for testing.

And the fact that the engine flush works with worn-out vehicles deserves praise on its own.

So we can't help giving this neat product a credit where credit is due.

In terms of drawbacks, we have touched upon them throughout the entire review. First and foremost there is the price. Since this engine flush is aimed primarily at the owners of older vehicles, we can't see many of these people paying such a steep price for this bottle.

The other complaint is that the results are nowhere near as good when we move to newer car models. Still, cleaning properties are rock-solid.


  • Works like a charm on older engines
  • Excellent cleaning properties
  • User-friendly
  • You can use it on both types of engines


  • Expensive
  • You can find more affordable alternatives

Golden Touch 1698 Fast Flush Engine Flush - 128 fl. oz.

Our Rating: 92/100

Now, this product is the polar opposite of the previous engine flush I have just covered. Oh, don't get me wrong, this flush also asks you to pay a very steep price. But, as a consolation prize, you do get one huge (128 ounces) bottle to play with.

But, let's start at the beginning.

This is the first product on the list that is engineered to work specifically with gas engines (domestic and imported). That means that the manufacturer had an opportunity to play with the formula and double down on some ingredients that work best with this type of engine.

So, what we have here is a petroleum-based flush that does not contain any ingredients like kerosene and mineral spirits that could potentially damage some parts of the engine, but does an incredibly satisfying job when it comes to cleaning and maintenance.

What do I mean by that?

Well, the product is very user-friendly and you won't need any help pouring the liquid before the oil change. Of course, as long as you are able to get around the size of the bottle. Repackaging the liquid into a couple of smaller bottles will definitely make this job far easier.

But, the main point is that this engine flush does a pretty good job at removing varnish, sludge, and deposits built up within the engine. But, this is the furthest this product manages to go. If you expect your old car will start flying after a single treatment. If you have to get the optimal results you need to play a long-term game and put a lot of care into engine maintenance.

To sum it up, this is definitely not the best engine flush the money can buy. But at this price point, you shouldn't really expect real-life miracles. But if you need an affordable way to keep the engine of your vehicle clean and healthy, easily remove the engine sludge, and do all that at a bargain price, you should take this bad boy into serious consideration.

If I was doing some ranking by categories this would definitely be one of the best budget picks.


  • Excellent budget pick
  • Ample package
  • Good long-term performance boosts


  • Lacks immediate results

Energy Release P023 Motor Flush - 15 fl. oz.

Our Rating: 93/100

Energy Release 9023 Motor Flush is yet another engine flush with an incredibly lucrative price tag. How lucrative? Well, I can say that for the price of one Liqui Moly, my overall winner of the roundup, you can easily buy two of these bottles. And, just for the reminder, the first product I have reviewed is not even the most expensive on the list.

In terms of formula and additives, the flush paints a pretty familiar picture with one noticeable difference. So, this product is your classic compound engineered to work with a diesel engine as well as the gas counterparts. You can probably guess from that formula doesn't lean too heavily in any direction, but does more than a competent jog at removing sludge and buildup while keeping the more sensitive parts of the engine safe.

Of course, at this price point, you should not expect any miracles and you probably won't experience major performance boosts in newer vehicles. But, the older engines may get a real kick out of this product.

One of the reasons behind this is that the engine flush contains anti-friction lubricant additives that don't make that much difference in newer units but do help worn out machines run faster. 

When I applied this liquid and performed the oil change, the change in performance was more than noticeable.

Speaking about the drawbacks, in this case, is not that sensible. I have already mentioned that the engine flush is not that productive in the case of newer car models. Still, that is not something you should really expect at this price point. Also, there are the inherent drawbacks of engine flushes engineered for multiple car models.

I would also say that the claims by the manufacturer that the engine flush increases horsepower and fuel efficiency are, to a large extent, misleading.

Be that as it may, this is by far one of the best engine flushes we have found in this price segment and can't offer anything but recommendations. If you own an older vehicle or like to change motor oil frequently so you can't afford a more expensive engine flush this is the product you are looking for.

Just make sure you know what you're buying.


  • Extremely affordable
  • Works well on older engines
  • Lubricative properties


  • Mild overall performance

Sea Foam SF-16 Motor Treatment - 16 oz. , white

Our Rating: 91/100

Sea Foam SF-16 Motor Treatment is yet another engine flush that tries to sway customers with an affordable price tag. But, as we all saw from a previous couple of reviews, high-quality compounds are not that uncommon even when you go down to the very bottom of the price ladder.

So, how does this engine flush bodes against this harsh competition?

Well, from what we all had an opportunity to see after extensive testing, a large number of customers will be a tall order for this one. That doesn't mean the engine flush is bad in its own right. On the contrary, you do get what is expected from a solid product in this price range.

What does that mean - the formula that is engineered for both major types of engines you can find on the market that offers solid cleaning properties but doesn't truly excel when it comes to boosting the real-life engine performance. But, what it sets out to do the engine flush does without too much hassle.

By that, I mean that you can easily use the product without anyone's help and since you are done with the oil change, the motor, injectors, cylinders and other parts of the fuel system should be devoid of less stubborn residue and sludge particles.

And to be quite honest, I have to admit that I was able to get slightly more mileage out of the motor oil. But that is how far this engine flush is able to reach. If you expect your car to run faster, work more silently, or squeeze out more horsepower, you will be left disappointed.

Bottom line - this is one decent engine flush that does provide reasonably competent maintenance performance and packs one very strong price-value ratio. If you are satisfied with that, give it a try.

But, keep in mind that you can find a couple of better engine flushes in this price range.


  • Very affordable engine flush
  • Solid cleaning properties
  • Spacious bottle (18 ounces)


  • Mild overall performance

High Milage Engine Flush Formula, Oil Cleaner for Cars and Truck, 15 Oz, STP

Our Rating: 89/100

On this list, I have already covered a couple of products that offered more than capable performance when it comes to older vehicles. This, however, is the first engine flush of the roundup that is aimed at owners of the vehicles with more than 75,000 miles under their wheels.

The problem with this one, though, is that while these previous engine flushes did offer reasonable performance upgrades when applied to older engines, in this case, the results are very mild. Let me explain what I mean by that.

STP High Mileage Engine Flush Formula does a very decent job when it comes to reducing accumulated sludge and varnish from the cylinder heads of your engine. After you pour in fresh motor oil the engine will come as close to coming off the factory line as it gets with the vehicle with such mileage.

I also have to mention that the price of this package is reasonably affordable (let's say the product sits somewhere in the middle of the price range) so you won't lose too much money if you give it a try and assess the results for yourself. Last but not least, the size of this bottle is pretty ample. 

With 15 ounces on disposal, you will get more than enough liquid to properly clean the vehicle that has been neglected for years.

Although reasonably strong, the liquid won't damage any sensitive parts and will prime the engine for a fresh batch of engine oil.

The real problem with this engine flush is that improving the performance of older vehicles is really not that hard with the proper mix of additives. Here these results are absent. Sure, the engine will become far cleaner and you will save yourself a lot of problems in the future but don't expect your old four-wheeler will become capable of fighting the uphill battles.

So, to sum it all up, this engine flush doesn't do anything particularly wrong and there is no danger you will accidentally damage the machinery. But, on the other hand, the results you are going to produce will remain forever tame so there isn't something to write home about, either. Make sure to take all this into consideration before buying.


  • Reasonably affordable
  • Efficiently cleans older engines
  • Ample size of the package


  • Performance boosts are all but absent

Niteo Motor Medic MF3 5-Minute Motor Flush - 32 oz, Multicolor

Our Rating: 80/100

Last but not least, we have Niteo Motor Medic MF35, an engine flush that sits somewhere in the upper areas of this product range. Well, at least when it comes to the price. This engine flush would get far more favorable reviews if it was sold under the $10 mark. As a silver lining, you do get a lot of liquid for the price you pay. But, the flush features some stiff competition even in this regard.

But, once again, we will start with the positives. Coming from Motor Medic, this engine flush is really fast-acting. I was able to get desirable results after only 5 - 10 minutes of keeping the engine running. That is pretty awesome and stands amongst the best times my team was able to produce during the entire roundup.

The second thing I really liked, in this case, is that the engine flush did manage to optimize the motor oil usage, especially in older vehicles. And, don't let us forget to mention one more thing - this engine flush works on all types of engines including non-turbo, turbo, and diesel engines. This is a small achievement since the product is completely safe and you won't damage any of the sensitive engine parts like gaskets on any of these types.

The real problem here is that the overall performance is pretty tame even if you take into consideration the price-value ratio. You will get your engine clan and primed for the change of engine oil, there is no doubt about that. But, in comparison with some other engine flushes in a similar price range, we can say that Motor Medic slightly dropped the ball with this one.

So this is pretty far the best engine flush you can find in the market at the moment. But, you do get solid cleaning results. That would earn our recommendation if not for the hefty price. This way, the only thing we can say is you can find far better alternatives.


  • Good cleaning properties
  • Fast-acting time
  • Works in all types of engines


  • Vert tame overall results

Best Engine Flush Frequently Asked Questions

What is the best way to clean sludge out of an engine?

In order to clean sludge out of the engine of your vehicle, you will need to use some of the engine flush products we have listed above. But, in terms of how to perform this task as easy and effortless as possible, here are steps you should take:

  • Remove the oil filter
  • Treat the motor with engine flush (pour it down the open hood)
  • Close the hood, start the car and let it run idle for 15 minutes
  • Turn off the engine and flush engine oil (remove the drain plug)
  • Install a new oil filter
  • Pour in fresh oil

And this is how to use an engine flush.

Will engine flush damage engine?

The short answer is no, but only as long you use an engine flush properly. What does that mean? First, a flush is not something you should use while driving. The agents will make the engine oil too thin. So, use these products only before replacing the oil.

Second, you need to carefully select the product type appropriate for the type of your engine. For instance, even if you buy the flush engineered for the appropriate type of engine, some formulas may prove to be too potent and abrasive for older units. If you are in doubt, ask your mechanic for advice.

How much engine flush should I use?

It really depends on the product and the size of the bottle. But, no need to worry - the manufacturer always indicates the necessary amount of flush on the back of the package. So, be sure to read the fine print. In most cases, however, you will need to use one bottle for engines under 10 quarts and two bottles for engines with oil capacities of 10 quarts or more.

After it's all said and done, we recommend:

As we already mentioned in the previous sections our pick for the title of the best engine flush on the market is without any doubt Liqui Moly 2037 Pro-Line Engine Flush. Sure, you are asked to pay a couple of dollars above the average. But, the price is still far from outrageous. What you get for this money is excellent motor cleaning, good priming for an engine oil change, and a noticeable vehicle performance boost. In our opinion that warrants the price.

After It's All Said and Done, I Recommend:

Liqui Moly 2037 Pro-Line Engine Flush

Our Rating: 95/100

Why it is the best?

  • This product comes from one of the most trusted brands available on the market
  • Works on both major types of engines
  • Excellent cleaning performance
  • Good priming for an engine oil change
  • Boosts engine performance
  • Not overly expensive
  • Amazon bestseller
  • Great customer feedback


So, we are finally at the very end of our short competition for the title of the best engine flush on the market. We hope the reviews were helpful. But, the best thing you can take away from this short read is that your vehicle's engine needs cleaning and maintenance just like any other part. Make sure to take this duty seriously. Using any of the engine flushes we have listed above is better than using none.

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