best radiator flush

The Best Radiator Flush: What to Look For & Best Options

Radiators are the unsung hero of the engine compartment. Without the radiator pumping coolant, your engine would die in a smoking mess. Coolant keeps your engine cool in the summer and warm in the winter. But to keep your cooling system running like a top, proper maintenance is crucial.

A proper flush of your car’s coolant on a regular basis (coolant flush) ensures an efficiently operating engine. While radiator flushes are a bit more complicated than an oil change, there are many products on the market that help facilitate the process.

Bottom Line Up Front

  1. Prestone Radiator Flush and Cleaner: Best Overall
  2. BlueDevil Radiator Flush: Economical Option
  3. Zerex Super Radiator Flush: Quick Cleaning
  4. Gunk Super Heavy Duty Radiator Flush: Fast Acting
  5. Irontite ThoroFlush: All-in-one Option

If you are looking for the best, all-around radiator flush, then Prestone Radiator Flush and Cleaner here is the best option. Compatible with all vehicles, this is non-toxic, a non-acidic cleaner that will scour your coolant system of all deposits, heavy metals, and other debris.

Prestone’s product is not a “quick” clean, as other flushes bill themselves. This product takes time to thoroughly course through the entirety of the system, from the radiator through the engine block and heater core. Once complete, you are left with an ultra-clean cooling system flush that will improve the performance of your vehicle.

Prestone AS105-6PK Radiator Flush and Cleaner | Advance Auto Parts

In my opinion, the best Radiator Flush is the Prestone Radiator Flush and Cleaner - it works with all types of coolant systems, its non-toxic, non-acidic and has a unique chemical makeup made to remove rust and heavy metals.

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Different Types of Radiator Flush

radiator flush

Not all radiator flush products perform the same once they enter your car’s cooling system. Cleaners, flushes, and additives all benefit your cooling system, but are added and behave differently.

Quick Flush and Clean

Many flush products are labeled “quick” because they are meant to drain right after you put them into the radiator. Any quick clean product will result only in a light clean. If your radiator has heavy rust or oily residue, then this is not the product for your cooling system.

Heavy-Duty Flush and Clean

Heavy-duty flush products rid your cooling system of everything that should not be there. Heavy metals deposited from the engine, rust and scale deposits, and oily residues all require heavy-duty cleaners. Vehicles using these products run them through the cooling system over several days. This allows the flush to remove deposits from all parts of the cooling system adequately.

Coolant Cleaner Additives

Many coolant cleaners are meant to work in combination with the coolant already in the system. This is very convenient for car owners, as it does not require a coolant flush. Buyers should be aware that they are the least effective cleaners and may affect the performance of the vehicle.

What to Look for In a Radiator Flush

There are several points to consider when purchasing a radiator flush:

  • Compatibility – many coolants are specific to the make of your vehicle, and even the year. Radiator flushes can also be make-specific. Be sure to read the label carefully to ensure the radiator flush product will work with your car or truck.
  • Type of Protection – radiator flushes offer all kinds of added benefits, from clearing out rust to removing oil deposits and other chemicals. If you know of any specific contamination in your coolant system, then you will want to purchase a product to tackle that issue correctly.
  • Location – where you live matters, because depending on the outside temperature, your coolant will behave differently. Hot climates may need a different type of flush than frigid climates.
  • Additive vs. Flush – many radiator flushes are just that – you put them into your cooling system after you’ve flushed the old coolant out. Other products are actually designed to go into your cooling system along with the coolant. When doing a flush, you do not want to purchase an additive.

A radiator flush is as essential as an oil change, although you will not perform a flush as frequently as an oil change. Depending on the manufacturer’s maintenance specs, they may call for a flush anywhere from 15 to 30k miles.

Similar to an oil change, a coolant flush is well within the capability of most vehicle owners. If you can change your oil, then you can change your coolant. The coolant plug is also underneath the vehicle and is relatively easy to access once the car is jacked up.

When using a flush, you will drain the cooling system twice with the radiator drain, once for the old coolant, and another time for the flush. When using a flush, be sure to read the directions carefully. Draining the old coolant and filling it with flush is not the only step. The cooling system flush has to cycle through the whole system. Each product will have specific instructions for how to flush a system with their product.

How to Find the Radiator Flush

radiator flush in car

When choosing the “best” radiator flush (or radiator cleaner fluid), there are a few key aspects to consider: the make and model of your vehicle as well as where you live. Before you purchase a radiator flush, be aware that there are two types: additives and flushes. An additive goes into your cooling system along with the coolant. Flushes go into the cooling system after you’ve drained the old coolant.

Once a flush is in your cooling system, it is typically meant to cycle through a few times before you remove it and add new fresh coolant. A key point to remember is that where you live can determine the type of flush you need. Corrosion is the most frequent issue in a cooling system. Modern car radiator options are aluminum, which is not prone to corroding. Over time, calcium and magnesium in the water portion of the coolant can form deposits, corroding the aluminum regardless of its anti-corrosive properties (corrosion inhibitor).

Therefore, if you live in a warm-weather climate, your coolant likely has a higher level of water. The more water, the more likely it is that corrosion could occur in your system. You will need a flush that is designed to eliminate deposits the cause corrosion, and any corrosive residue already present.

Cold weather climates also can cause corrosion, but cold weather vehicles typically have higher ratios of antifreeze to water. Antifreezes have more corrosion reducing properties, unlike water, and the higher ratio will result in less corrosion. On the other hand, water can freeze in ultra-cold climates, damaging hoses and causing harmful buildup in the cooling system.

All car’s radiator flushes have chemicals. Some may not be appropriate for your vehicle. Read the details on the rear of the packaging to make sure a flush works with your car.

Top 5 Picks for the Best Radiator Flush

#1 – Prestone Radiator Flush and Cleaner


Prestone’s radiator flush product is the winner, and it has a lot to do with the name. If you go to your nearest auto parts store, one of the most common brands of antifreezes on the shelf is Prestone. Thus, when it is time to flush your system, it pays to trust the brand that makes the actual coolant.

One of the best aspects of this radiator fluid cleaner and flush is that it produces a “super-chelating” reaction in the cooling system of your vehicle. Chelation is when specific ions in a solution bind to heavy metals. Prestone Flush and Cleaner have chelating ions that bind to rust and other heavy metals in your cooling system. When flushed, the metals disappear with the solution.

Since the product comes in a 22-ounce bottle, only one is necessary unless your vehicle’s cooling system is over 3 gallons, which is not common. The entire bottle gets poured into the cooling system after the old coolant drains completely via the drain valve. Ions and compounds in the product bind to rust and scale, eliminating them from the cooling system.

Another aspect of this product is that it lowers the pH of the entire system. When heavy metals and scale leaves the radiator and engine, the new coolant avoids the acidic deposits. Less acid means less corrosion, protecting your engine, radiator, and hose connections.

Heavy-duty cleaning is possible with this product. Prestone recommends that drivers keep the product in their coolant systems for several days, flush, use another bottle, and repeat. Light-duty flushing implies only one flush, which is sufficient for most systems. Due to the chemistry of the product, Prestone can offer deep cleaning to eradicate the system of metals and other debris.

Metals and scale reduce your car’s ability to transfer heat from the engine to the coolant. If rust takes up space that is typically used by coolant, then that leaves less surface area for the coolant to absorb heat. Over time, this could lead to overheating and engine failure.


  • Two-types of cleaning: light and heavy duty
  • Unique chemical makeup with chelating ions, made specially to remove rust and heavy metals
  • Works with all types of coolant systems
  • Non-toxic and non-acidic


  • Heavy-duty flush requires the purchase of two bottles
  • Pricier than other comparable radiator flush solution products
Prestone AS105-6PK Radiator Flush and Cleaner | Advance Auto Parts

In my opinion, the best Radiator Flush is the Prestone Radiator Flush and Cleaner - it works with all types of coolant systems, its non-toxic, non-acidic and has a unique chemical makeup made to remove rust and heavy metals.

Check Price Buy at
We earn a commission if you click this link and make a purchase at no additional cost to you.

#2 BlueDevil Radiator Flush

blue devil

BlueDevil offers an economical product that performs like a premium product. Specifically for high-mileage vehicles, BlueDevil uses a highly concentrated product to clean your radiator and cooling system. One of the most attractive features of this product is the size. It comes in a 32-ounce bottle, which is enough to flush all sizes of cooling systems.

BlueDevil promises that it can remove all types of grime and dirt from your vehicle’s cooling system. The directions recommend that you not only drain your radiator but the entire system. Remember, there is coolant in the engine block, heater core, and hoses as well.

When using this flush, the directions indicate that the ideal way to flush the entire system is to drive for 3-6 hours after using the flush and before putting in the new coolant. This way, all areas of the system are able to cycle the product and get rid of the dirt and grime.

Made in the USA and able to work with all types of vehicles, BlueDevil is a versatile yet straightforward flush. Online, BlueDevil offers excellent instructions and videos to complement their product. Users can watch professionals flush their vehicles step by step, which makes using the product that much easier.

See how BlueDevil Transmission Sealer Performs in our full review here.


  • Comes in a large bottle, negating the need for two
  • Economical compared to other brands
  • Clear directions provided on package and online
  • Formulated for dirty, high mileage vehicles


  • Does not specialize in removing metals and scale
  • The product does not offer a heavier-duty cleaning option
BlueDevil Radiator Flush | Advance Auto Parts

Our specially formulated flush works well in all vehicles, especially those with high mileage warranting a deep clean.

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#3 Zerex Super Radiator Flush

zereh flush

Zerex provides a unique product for those looking to do a radiator flush, but don’t have all day, or days, to do it. In ten minutes, Zerex promises you can use their product and then move on with your life. While not specifically for heavy-duty cleaning, Zerex gets rid of everyday grime and dirt common to all cooling systems.

Quick cleaning is all most cooling systems will need. Modern cooling systems, particularly in the last decade, are aluminum and use less overall coolant than in the past. This results in less corrosion. Therefore, most car owners only need light cleaning in their cooling systems.

While occasional debris will not harm your engine’s ability to function, it will make it less efficient. Coolant that has debris in it will not be able to remove the maximum amount of heat from an engine. When engine heat dispersion is not optimal, the engine heats up more and has to work harder, affecting gas mileage.

Another critical aspect to consider is that Zerex is effective in removing oily residues. Coolant in the engine block moves exceptionally close to the cylinder heads. Cylinders move because oil lubricates them. If a cylinder head gasket cracks, then motor oil can leak into the coolant within the engine compartment.

When oil gets into the cooling system, it leaves a residue that is hard to remove. Think about cleaning an oily pan in your sink – it takes lots of scrubbing to remove that film. Your cooling system is no different, which makes Zerex’s formula beneficial to those with oily coolant systems.


  • Made to work in all aluminum-based coolant systems
  • Fast application and results make for a convenient flush
  • Cleans oil residue, which can impede the flow of coolant through the engine
  • Zerex is made by Valvoline, a reliable brand


  • Only provides quick cleaning, heavy-duty cleans require a different product
  • Quick clean may not remove debris from the entire cooling system
Zerex Super Radiator Cleaner | Amazon

Heavy-duty patented formula helps remove radiator solder bloom, rust, scale and other deposits that flushes miss.

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We earn a commission if you click this link and make a purchase at no additional cost to you.

#4 Gunk Super Heavy Duty Radiator Flush

motor gunk

Gunk offers a straightforward all-in-one radiator flush solution that is economical and easy on your cooling system. Although Gunk is not known for its coolants and antifreeze, they are known for making quality cleaners and degreasers.

Gunk is made to work with all vehicle cooling systems, eliminating the need to purchase a make-specific radiator flush. As well, this flush is meant to work quickly. This means that you will not spend days filling and draining your system, over and over. One bottle of Gunk and an hour or two of your day is all that you need.

Chemically, this product is non-acidic. Acids will cause corrosion in your radiator and heater core. A good radiator flush that is even mildly acidic is not a good idea, because it will negate the beneficial effects of the flush. A radiator with corrosion will not disperse heat as well, resulting in an engine that overheats.

While this is a product made for quick use, it still removes rust and scale. As well, it does not necessitate the purchase of distilled water to use alongside via a water pump and flush. Gunk offers a solution that is easy on the cooling system while removing stubborn debris.


  • Does not require distilled water as part of the flush
  • Works quickly, while still removing rust and scale
  • For use in all makes and models
  • Made for aluminum radiators and cooling systems


  • Does not offer a heavy-duty cleaning option
  • May not clean the entire cooling system, such as in the engine block
Gunk C2124 Radiator Flush | Amazon

Contains only mild organic acids that act as cleaning agents removing rust deposits and oily residue.

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03/09/2024 10:50 pm GMT

#5 Irontite ThoroFlush


ThoroFlush is an all-in-one product that includes flushing the radiator and cooling systems. Since this product comes in a concentrated powder, it is easy to mix with various amounts of water to achieve different results.

Mixing ThoroFlush with some distilled water and pouring the entirety into the radiator is the first step when flushing a radiator. Then, pouring more water into the radiator until it fills. Running the engine and continual refilling with water then cleans the entire system out. The flush and water drains and the new coolant goes in. Irontite makes the process very simple.

Many of today’s domestic vehicles require Dex-Cool, which is a non-glycol type of coolant that is supposedly easier on the engine. The composition of Dex-Cool still results in deposits, mainly if regular antifreeze mixes with Dex-Cool. ThoroFlush is made to break down those deposits and carry them away.

Another attribute of ThoroFlush is how it cleans heater cores. Heater cores are much smaller than radiators. They are prone to failure as they fill up with debris faster. Thoroflush removes debris and rust from heater cores, which will then allow you to have heat in your vehicle.


  • Ultra powder concentrate that is useful in many different applications
  • Cleans the most modern types of cooling systems, such as Dex-Cool
  • Helpful in cleaning oil coolers in diesel engines
  • Requires flushing your radiator only once


  • Requires mixing with distilled water
  • Does not claim to work on all models and makes
Irontite ThoroFlush | Amazon

One pint of lrontite Thoro-Flush will clean and strip the Ethanol Gel, Scale, Rust, Bio Diesel Residue along with other contaminates out of a fuel tank with a simple flush. 

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02/19/2024 09:35 pm GMT

Comparing the Options

Brand  Use on all vehicles  Heavy Duty Clean  Size (oz.)  Price  
Prestone  x  x  22  $$ 
BlueDevil  x    32  $ 
Zerex  x    22  $$ 
Gunk  x  x  22  $$ 
ThoroFlush    x  16  $$$ 

Frequently Asked Questions

Is flushing the radiator necessary?

Yes. Most of the time it is necessary to flush the radiator when you’ve driven at least every 25,000 to 30,000 miles or reread your owner’s manual for recommended mileage.

Can a radiator flush cause problems?

Certainly. If the radiator flush is not changed when it’s needed or according to your owner’s manual it can cause damage to your engine, so, you better flush the radiator.

When do you need to flush your radiator?

There are several signs that your car needs a good radiator flush. For example, if your car is overheating it maybe a sign that you need a radiator flush, however, you should check if your coolant level is okay, and if it is, then you probably definitely need to flush your radiator.

Other critical signs are coolant leakage underneath your car, grinding noise coming from the engine as well as steam or an odd smell, and visible debris in your coolant.

Final Thoughts on Radiator Cleaning Flush

Choosing the best overall radiator flush depends on your vehicle and where you are driving. Older, high mileage vehicles are likely going to need a heavier-duty clean that only the Prestone can offer. Cars that have lots of miles are prone to rust. Moisture gets into engines and radiators over time, causing corrosion and rust. If it builds, the engine will overheat.

Vehicles in cold weather climates will also need a heavy-duty clean. If the vehicle is newer, then the Gunk or ThoroFlush is also an option. They remove stubborn metal and rust deposits, but without as much flushing and refilling. Irontite’s product works with Dex-Cool engines, which is a bonus.

For those on a budget, BlueDevil’s flush is a good, basic option. It works quickly, comes in a large bottle, and is cheap. It does not offer some of the cleaning power that Prestone or Gunk does. But, it is a good option for maintaining the cooling system of a newer car on a regular basis.

Prestone AS105-6PK Radiator Flush and Cleaner | Advance Auto Parts

In my opinion, the best Radiator Flush is the Prestone Radiator Flush and Cleaner - it works with all types of coolant systems, its non-toxic, non-acidic and has a unique chemical makeup made to remove rust and heavy metals.

Check Price Buy at
We earn a commission if you click this link and make a purchase at no additional cost to you.

Last Word on Radiator Cleaner

When choosing a radiator flush, make sure you take into consideration the type of car you have, how many miles it has, and where you are driving it

Cooling systems need regular maintenance, regardless of who, where, or how you drive. Keeping the engine at a consistent temperature ensures the engine does not stress and keeps your gas mileage down. It also ensures you stay warm by keeping your heater running at full capacity.

An engine is the heartbeat of a vehicle, and coolant makes sure the engine beats optimally. Regular flushes (with Radiator cleaner), according to the manufacturer’s specifications, is the best way to keep your car running for a long time.

Further Reading on Auto Maintenance:

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