The Best Additive To Quiet Engine Noise of 2020

If your noisy engine drives you crazy, consider an engine treatment before spending a fortune at a mechanic shop. The Liqui Moly engine flush is miles ahead of the competition because it cleans, lubricates, and protects your engine, no matter whether the engine is gasoline or diesel.

Top 4 Best Engine AdditivesWhy It's BestRating
Liqui Moly Pro-Line Engine FlushInexpensive, cleans, lubricates, protects, compatible with diesel and gas engines★★★★★
XADO Oil Additive for Worn EnginesSpecially formulated to treat worn metal, protects, extends life of vehicle★★★★★
Bar's Leaks Engine Repair TreatmentSeals leaks, cleans, lubricates, protects★★★★★
Liqui Moly Hydraulic Lifter AdditiveInexpensive, cleans, lubricates, protects, ideal for older vehicles★★★★

Best Additive To Quiet Lifters and Other Engine Components

Liqui Moly Hydraulic Lifter Additive to Quiet Knocking

Image of the Liqui Moly 20004 Hydraulic Lifter Additive

The Liqui Moly hydraulic lifter additive improves lubrication in the oil, which can be a great way to quiet engine problems caused by hydraulic tappets, such as engine knocking. Ensuring all components glide together in harmony will allow you to drive in peace for hundreds or even thousands of miles.

In addition, carbon gunk accumulates over time in tappets, which can cause them to lock up and malfunction. This additive works by clearing out gunk, thus making the tappets run smoothly.

Each 300 milliliter bottle of Liqui Moly additive restores 6 liters of engine oil. Certain engines may require more than one bottle of this product. Further, the additive is compatible with all oils on the market.

The additive works with vehicles with turbochargers or catalytic converters.

Liqui Moly Pro-Line Engine Flush

Image of the Liqui Moly 2037 Pro-Line Engine Flush - 500 Milliliters

The Liqui Moly engine flush is usable in both gasoline and diesel engines. Further, it can be used in vehicles with catalytic converters.

To use it, simply add it to the engine oil before an oil change. Let it settle by idling the engine for 10 minutes. You then drain the oil, change the filter, and add more engine oil.

The engine flush performs a variety of functions. It is a detergent, so it cleans out sludge and built-up debris. Further, it prevents corrosion and improves oil’s lubricating abilities.

All of these functions help make an engine as quiet as possible by optimizing its performance.

Bar’s Leaks Engine Treatment for High-Mileage and Older Engines

Image of the Bar's Leaks Engine Treatment Specially Formulated for High-Mileage Engines - 16.9 oz

The Bar’s Leaks engine treatment is an incredibly easy to use treatment for your vehicle. The only step is to add 1 bottle to the oil per 4 to 6 quarts of oil. It will then gradually remove residue and grime from valves, tappets, and other components as you drive.

Since the formula is made for older and higher mileage vehicles, it can remove years worth of sludge from the engine. Sludge can make engines noisier because it stops up components and blocks valves. This can, for example, cause noisy tappets.

This treatment is also great for preventative maintenance. Instead of waiting for your car to start clattering, use the treatment right before every oil change. It can increase the longevity of a vehicle and keeps rides smooth and quiet.

Mobil 1 V-Twin Synthetic Motorcycle Motor Oil

The Mobil motorcycle oil is specially formulated for use in motorcycles. This oil can withstand the extreme heat produced by motorcycle engines, even in the middle of summer. I expected a specialized type of oil to be significantly more expensive than conventional types, but this product is quite affordable.

This oil provides better lubrication and may increase the longevity of your motorcycle engine.

However, do keep in mind that this oil won’t be a magic fix to quiet an engine if you were already using an adequate quality oil. You will likely only hear a significant difference if you were using a poor quality, low grade oil.

Bar’s Leaks Engine Repair

Image of the Bar's Leaks Engine Repair - 16 oz

The Bar’s Leaks engine repair treatment performs a variety of functions. First and foremost, of course, is its ability to seal in leaking oil.

It also cleans inside the engine. Built up gunk is usually responsible for making an engine noisier, so cleaning the engine is a great way to make it quieter.

Further, the treatment improves your oil’s ability to lubricate, which helps prevent locked up components and malfunctions. This can also reduce wear, which adds longevity to your vehicle.

However, this treatment may not be a long term solution. To stop leaks completely, it may be necessary to replace gaskets or do other repairs. If you still notice minor leaking after using this product, something more intensive is likely necessary to repair your car.

Rislone Nano Prime Synthetic Engine & Oil Additive

Image of the Rislone Nano Prime Synthetic Engine & Oil Additive - 16.9 oz

The Rislone Nano Prime oil additive is an engine treatment that you add to your oil to obtain a host of benefits. It both treats and protects metal from friction, which reduces wear and can add years to your engine.

Added lubrication is also a good way to quiet a noisy engine.

It also clears away built up sludge in an engine, which can further silence engine noise.

Each bottle of this product treats 4.5 to 7 quarts of oil, so a single bottle will be sufficient for the vast majority of engines.

Due to the added efficiency that extra lubrication gives, the treatment may also make your vehicle more fuel efficient.

XADO Engine Oil Additive for Worn Metal Surfaces

Image of the XADO Engine Oil additive - Protection for Engines - additive for wear Protection & rebuilding of Worn Metal Surfaces - Metal Conditioner w. Revitalizant 1Stage Maximum SUV (up to 10qt of Oil Capacity)

The XADO engine oil additive was created to treat worn out or rusty metal.

Metal can get worn out in a variety of ways; it could be worn from subjecting it to rough environments or simply due to high mileage. Whatever your situation, this metal conditioner works on trucks, SUVs, and cars by placing a ceramic metal coating over your worn out metal components.

The coating both compensates for your existing metal and protects it from further harm in the future.

Rusted out parts can increase friction and cause clattering and other noises, so repairing old metal may be an effective way to silence a vehicle.

To use this treatment, add it to the oil. Start the engine and let it idle for a few minutes. It may take several hundred miles of driving before you notice the effects of this product. 1 bottle is sufficient for oil capacities of up to 10 quarts, which should be enough for almost all engines.

Make sure to apply this product in a warm environment or it may be clumpy and difficult to handle.

You will likely only see or hear the effects of the XADO engine additive if your engine has significant wear to it. If your vehicle is newer or well maintained, then you may wish to look for another product to quiet your engine, as this may not do much.

Marvel Mystery Oil Treatment

Image of the Marvel Mystery Oil MM12R - 16 Fl Oz. (Pack of 2)

The Marvel Mystery oil treatment is used to clean out fuel injectors and carburetors, and it overall helps keep engines free of sludge.

It also keeps the quality of oil intact by preventing oil breakdown in extreme conditions.

By improving lubrication and stopping valves from sticking, this oil additive can make vehicles quieter.

The manufacturer recommends that you replace 20 percent of your oil with this additive. You should repeat this process after every oil change for the best performance.

The additive is compatible with virtually all oil types, from conventional to synthetic. It can be used in gasoline, diesel, and ethanol blend engines.

Sea Foam Motor Treatment

Image of the Sea Foam SF-16 Motor Treatment - 16 oz.

The Sea Foam motor treatment is one of the best known engine additives on the online market due to its affordability and functionality. It’s a detergent, meaning it clears residue and other carbon gunk all throughout the engine, including valves and cylinders. You can also put it in the crankcase to clean out residue.

Another use is putting the Sea Foam motor treatment right into your gas tank. This helps lubricate and clear the fuel system, which improves the performance of your vehicle.

Not only does it clean, but it also provides lubrication to upper cylinders, which makes your vehicle run more efficiently. This can make your vehicle quieter and give you better gas mileage.

Hot Shot’s Secret Diesel Engine Fuel Additive

This Hot Shot’s additive is specially designed to work in all diesel engines. You should put a 16 ounce bottle of this product in your gas tank per 40 gallons of gas once every 6 months. The additive circulates throughout your entire fuel system, cleaning cylinders, lines, and tanks.

The additive does more than just clean your fuel system. It also removes excess moisture and lubricates the fuel system. Lubrication is a great way to restore silent operation to noisy and clattering vehicle components.

The treatment also contains cetane, which helps fuel to ignite under compression. This can make your diesel vehicle more efficient, and it may even give your vehicle better fuel efficiency.

Rislone Engine Oil Supplement with Zinc for Older Engines

The Rislone oil supplement contains zinc, which older engines need to run properly. Recent regulations mean that it is harder to obtain motor oil with zinc, and modern vehicles generally do not require zinc because they use a rolling camshaft.

However, older engines experience more wear from their tappet camshaft. Thus, the zinc is needed to bind with the existing metal and form a protective layer. Without zinc, your engine will wear out faster, and it may get noisier the worse the damage gets.

The Rislone supplement adds zinc to your vehicle’s oil without having to replace all the oil with oil that contains zinc. By using this additive, you may increase the longevity of your older, high mileage car, and you’ll keep it as quiet as possible as well.

Lucas Oil Heavy Duty Oil Stabilizer

The Lucas oil stabilizer is suitable for use with any oil, from synthetic to conventional. It can also be used with newer and older engines.

It is a multipurpose additive. The Lucas Oil stabilizer is 100 percent petroleum, so rest assured that it will better lubricate your engine than just oil alone. The reduction in friction will also cause your engine to run cooler and prevents wear.

Of course, increased lubrication makes your engine as quiet as it can be. It can get rid of knocking, smoke, and other problems caused by malfunctions and overheating.

Lastly, it may increase oil pressure, which makes your vehicle perform better at higher speeds.

The manufacturer recommends using 1 quart of this product per gallon of motor oil. For high mileage and worn out engines, they recommend using about triple the amount.

BG MOA Engine Oil Supplement

The BG MOA engine oil supplement clears carbon sludge and other gunk from your engine that are a result of oxidation. Further, the additive prevents oil from thickening, which stops more sludge from building up and slowing down the engine.

The benefits are that this additive increases the lifespan of your vehicle, and it can save you money down the road in maintenance fees and mechanic shop visits.

Buying Considerations for Additives

With how many types and varieties of engine additives there are available online, it’s worth your time to consider your vehicle’s situation to get the best product possible.

Diesel or Gasoline

Diesel and gas engines are very different. As you may be aware, diesel engines do not have a spark plug to ignite fuel, and instead they rely on compression to combust fuel.

Further, additives can contain different materials to tackle the unique problems of diesel and gasoline engines. For example, some diesel engine additives contain cetane, which helps fuel combust under pressure.

The online market for diesel engine additives is a bit smaller, but there’s still a solid variety of options out there. The Hot Shot’s Secret diesel engine additive both cleans and lubricates your engine. Cetane is also an ingredient, which is a great way to improve fuel efficiency.

Another choice for owners of diesel engines is the Liqui Moly Pro-Line engine flush. It is one of the few good options that are suitable for both diesel and gasoline engines.

Older versus Newer Engines

Your vehicle’s age and mileage are other crucial considerations when purchasing an additive.

For newer cars, your focus will likely be on preventing wear and tear. In that case, all you’ll need is a lubricant to keep things smooth and functional. The Sea Foam motor treatment is a versatile, effective, and inexpensive oil or fuel system supplement for people looking to lubricate and protect their engines.

As your vehicle’s mileages increases, so does its number of problems. It’s important to pinpoint the source of the problem (e.g., a noisy tappet). Otherwise, you may waste money buying additives that you didn’t need.

For worn out metal, the XADO oil additive both treats and protects metal from further harm.

Some old, high mileage engines are designed to need zinc in oil. However, most modern oils do not contain zinc due to environmental regulations.

You can navigate this by purchasing an additive that contains zinc, which binds to metal surfaces and protects them like a second coating. The Rislone engine oil supplement with zincis a great way to introduce that ingredient to your engine.

Some older engines do not have specific problems, but they still need a supplement. In that case, the Bar’s Leaks additive for older engines is a great product that is a catch all. It cleans, lubricates, and protects your high mileage vehicle.

Your Vehicle’s Unique Problems

Some motor additives can sound like a panacea. The manufacturers claim they can fix all your car’s woes if you simply buy their product. As you may suspect, this is only marketing.

It is important to identify the source of your vehicle’s noise or other ailment. In older vehicles, you may hear a characteristic “knocking” sound caused by malfunctioning hydraulic tappets.

Clanking and other noises can be caused by many things. Some common culprits include worn out metal, built up carbon sludge, and a lack of lubrication. If you can’t identify which of these 3 is the culprit, you may want to consider purchasing a multipurpose additive.

For example, look for one that is both a detergent and a lubricant. this will both clean your engine and make it run more smoothly. There are quite a few products in the above list that perform a variety of functions to help you quiet your engine.

If, however, after driving for several hundred miles with your additive and your engine still makes excessive noise, you may have to bite the bullet and go to a mechanic. Unfortunately, there are some problems that additives cannot address.

FAQs About Engine Additives

Which engine additive will make my vehicle quietest?

The answer to this question all depends on your engine’s problem. If your vehicle is older and you hear a distinct knocking sound, this may be due to a problem with your hydraulic tappets. The Liqui Moly additive for hydraulic tappets may quiet your engine.

If your vehicle makes clanking sounds or is simply noisy, that may be due to insufficient lubrication or wear to the metal. A build up of sludge is another culprit.

If you think that your problem may be a lack of lubrication or sludge build up, the Rislone Nano Prime additive is a multipurpose solution that could mitigate these issues, which will make your engine quiet again.

If you suspect that your metal is corroded or worn out, This XADO oil additive will help restore your engine’s metal.

What causes engine knocking, and how can I stop it?

Lots of engine problems can cause knocking. For older engines, there may be a problem with a stuck tappet. Tappets control the valves that direct the intake of air, so if one malfunctions, that can cause a whole host of problems.

Liqui Moly makes an additive that seeks to address this common issue in older engines.

For newer engines, you may have a faulty spark plug. Obviously, an oil additive cannot fix this issue, so you will have to take your vehicle to the mechanic to get that fixed.

Carbon sludge deposits may also cause this distinct sound. Luckily, additives may help with this issue. most of the additives on this list contain detergents that will clear your cylinders of gunk, thus making your car much less noisy.

What additive is best for noisy lifters?

Before talking about additives, make sure you’re maintaining a basic standard of care for your vehicle. Regular oil changes and oil filter changes will be your best bet to stopping lifters from causing a racket.

if your vehicle is well maintained and your lifters are still too loud, then you will want to consider an additive. Liqui Moly makes an additive especially for hydraulic lifter care, so you may want to consider this product.

However, any well regarded additive that cleans, lubricates, and protects your engine will also treat your noisy lifters. I recommend the Bar’s Leaks engine repair treatment, as it provides all the benefits you would expect of an engine treatment.

You may need to drive several hundred miles before you see the full effects of an engine additive. This is because it needs to circulate throughout your engine

Keep in mind that a treatment or additive can only do so much for your lifters. It’s possible to still hear excess noise even after changing your oil and oil filters and using an additive. If you still experience annoying sounds after trying all these steps, your next best step is to contact a mechanic shop.

Is thicker or synthetic oil necessary for me?

Instead of using an additive, you may be wondering if it is worth it to change your oil brand altogether. The answer is that it depends.

It is true that synthetic oil is generally superior to conventional dinosaur oil. It doesn’t degrade even at extreme conditions and is less likely to clump. Since synthetic oil does not build up deposits like organic oil does, it keeps engines quieter.

However, it tends to be expensive compared to organic oil, so you have to decide if the benefits are worth the cost.

As a general rule, follow the recommendations set forth in your owner’s manual. Synthetic oil is more likely to be recommended for newer engines. Older engines generally do not benefit from synthetic oils, and they may in fact be harmful to your engine. This is because synthetics do not contain ingredients that your older car may need, such as zinc.

One advantage of synthetic oil is that it flows much better than conventional oil in the winter. You may wish to switch up to synthetic oil, even if it is just to withstand the coldest winter months. At the opposite end of the spectrum, synthetics also perform well during blazing hot summer months.

For oil viscosity, again, check the manual. The manufacturer will recommend the oil viscosity that works best for your vehicle.

You may wish to switch oils if you live in a region with harsh winters. For example, you can switch to a 5W oil when it’s cold, which will keep your engine running despite the frigid weather.

Generally, however, modern oil adapts well to changing temperatures. As such, switching to either a thicker or a thinner oil is likely not necessary for those that do not live in extreme climates, as it will not make much of a difference.

Final Word

Scrolling through the endless amount of engine additives and treatments available online can feel like a barrage of information. You may even be wondering if additives do anything useful, or if they’re just scams and marketing.

Like many things, engine additives lie somewhere in the middle of the spectrum. They will not be a miracle cure all for your vehicle, but they aren’t all snake oil either. Additives truly can decrease the noise output of your engine if your engine has problems that they can address.

Oil clumping, wear and tear, and friction are all issues that additives can help solve. If you believe that you have at least one of these problems, consider an additive to see if it will help solve these issues and thus quiet your vehicle.

For oil clumping and carbon deposits, any additive that is a detergent (i.e., has the ability to clean) will clear away pesky sludge. Almost all of the products on this list have cleaning abilities, but double check by reading the description to make sure you’re buying a treatment that is in fact a detergent.

For metal wear and tear, look for an additive that promises to treat and protect metal. This additive product by XADO will help fix problems caused by worn out metal.

If you have an old engine, your wear and tear may be caused by a lack of zinc in your oil, as modern oil generally does not contain zinc. Rislone makes a supplement to your oil that contains zinc, which binds to metal and protects it from further harm. However, zinc can be an environmental pollutant and a hazard, so make sure that it is safe to use in your area and use it with caution.

Lastly, if your noisy engine issues are caused by a lack of lubrication, then you’re in luck. Virtually all engine additives add lubrication to your engine. The Lucas Heavy Duty oil stabilizer is a great, inexpensive lubricant with no bells and whistles, as it is just pure petroleum.

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Kelly Brayton
I'm a senior Chemical Engineering student at Purdue University working as a teaching assistant and a researcher. I enjoy helping people learn and better their lives by writing about technical subjects.

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