Reviews

The Best Radiator Flushes: Keep Your Radiator Running Clean

Lengthen the life of your car with these top radiator flush products.

Entering our 7th season of /DRIVE on NBC Sports, and with millions of YouTube and Facebook followers, The Drive is a leading authority of all things automotive.

The Drive on NBC The Drive on YouTube The Drive on Facebook

The Drive and its partners may earn a commission if you purchase a product through one of our links. Read more.

BY Corrina Murdoch / LAST UPDATED ON April 26, 2021

Flushing your radiator once in a while is an essential part of overall vehicle maintenance. The radiator is the part of your car responsible for thermoregulation. When the radiator works properly, it'll keep the engine cool while you drive so it won't overheat, and you'll get a smooth ride. However, if the radiator gets too gunked up by rust or debris, your ride will get the mechanical version of a fever. Too hot to touch, you'll be standing by the side of the road with smoky steam emanating from your engine as you rue the day you forgot to use the radiator flush.

To help you, we have tracked down the best radiator flush solutions on the market. This breakdown details everything you need to know about finding the proper radiator flush: from how the chemicals strip away grime to what you need from a radiator flush, we've compiled the essentials right here.

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.

Learn more

Benefits of Radiator Flush

  • Keep your cooling system running properly. Your coolant system can easily become clogged by scale, grease buildup, and other debris that gets into the system. Using the best cooling system flush for your radiator can help remove these obstacles to keep the system running properly.
  • Help improve engine efficiency. Your radiator pumps coolant into your car’s engine, keeping it cool and preventing it from overheating. Without it, your engine would suffer and work much harder than it should. Radiator flush can help prevent debris from clogging your engine. Much like a person who has been running for a long time in heat needs their body to cool itself by sweating and pumping blood through your heart, your car’s engine needs its radiator to help keep it cool.
  • Lengthen the life of your vehicle. Letting your car run for years and years without flushing your radiator can allow buildup and blockage to take place. By cleaning your clogged radiator, you can help lengthen the life of your car by keeping the engine and cooling system running clean.

Types of Radiator Flushes

Liquid Flush

Easily the most common type of radiator flush, liquid flushes are also the most intuitive category. Ideal for those new to radiator maintenance, some are concentrated while others require you to pour them in. Per the flush namesake, it works in conjunction with water to remove rust, corroded particulate, and oily residue. Usually, the active ingredient is sodium citrate, a buffer against acidic conditions. Many include moderate corrosives and catalysts to facilitate the chemical reaction. 

Powder Solutions

Though they aren’t as prevalent, powder solutions offer a unique advantage: you can control the intensity. Yes, it takes an extra step and requires a bit more work, but you can control the dilution. Keep in mind that the powder can be challenging to manage without the proper equipment—it is harsh on the skin and, even worse, on the eyes. However, it is very powerful at stripping away grease and rust. Plus, the shelf life is much longer on powder than it is with liquid solutions. 

Pressure-Based

In addition to chemical formulas crafted to eliminate debris, there is another type: pressure-based. These radiator flushes use the force of air and water pressure to eliminate debris. It has the benefit of being gentle on hardware; and, unlike chemical approaches, won’t burn skin or harm eyes. You can find hose attachment wands that scrape debris out of the way. While these are best used in conjunction with occasional chemical flushes, you can use them more frequently than other types without damaging the radiator.

Top Brands

Prestone

Opening its doors in 1927, Prestone has a proven track record of quality vehicle fluids. Roughly 90 years ago, it hit the ground running by inventing the world's first non-flammable ethylene glycol. Since then, Prestone has expanded its repertoire to include brake fluid, rust-removing chemicals, and more. Among its best-favored offerings is the Prestone Radiator Flush and Cleaner, an effective way to keep your car's thermoregulation in good condition. 

IronTite

Commencing operations in 1952, IronTite began its work by crafting coolant chemicals for machine shops. Though it remains a relatively small business, it puts an enormous amount of focus on chemical engineering. The result is high-quality cooling system flush solutions and all-weather sealants for a variety of vehicles. One of its top products is All-Weather Seal, a formula that prevents damage to the coolant system. 

Gunk

A proudly American company based out of North Carolina, Gunk is known for its high-end degreasers and automotive cleaners. Innovating its formulas to meet today’s evolving vehicle tech needs, it continues to be a major name in professional racing. Popular amongst home mechanics and racetrack enthusiasts, its Gunk Radiator Flush is used to eliminate debris and rust. 

Evaporust

An international name in rust-removal, Evaporust has a wide range of brand names under its umbrella. These include Thermocure, Rust-Block, and Safe-Erase. Living up to its products’ names, this company creates safe, eco-friendly formulas that are good for the environment and the mechanic. Among its top selections is the Evapo-Rust Super-Safe Rust Remover, a powerful yet gentle formula. 

Radiator Flush Pricing

  • Under $20: Radiator flush in this price range will usually be a liquid and often be fairly diluted. These flushes usually come in either 22 or 16-ounce containers and work for both corrosion and grime. 
  • Between $20 and $40: The vast majority of radiator flushes come in this range, with most powders and high-end fluid formulas falling in this category. The price reflects an increased quantity of active chemicals, making these better suited for serious radiator wear.

Key Features

Active Chemical and Intensity

The idea behind radiator flush is always the same: to eliminate caked-on grime and rusted particulate. However, not all chemical formulas are made alike. Depending on the active ingredient — and how much of it is present in the solution — it will cause a different effects. The most common ingredient is trisodium citrate. The citrate converts into citric acid when exposed to water, stripping away debris and interacting with residue from radiator fluid. Other versions of the chemical include sodium formate and sodium acetate. The more active chemical in the solution leads to more powerful rust removal, though it is more likely to damage the hardware. Be sure to check the specs on your radiator flush and familiarize yourself with its potency. 

Application Method

Depending on the radiator flush you’re using, you may have to dilute it yourself. Alternatively, it will come as a pre-mix. There are unique benefits to each approach: powder and concentrated liquid options let you control the potency, but they carry a greater risk of harming your skin. Pre-mix is usually cheaper and less potent but far easier to use. However, because they are less powerful, you may have to repeat the process a couple of times. If you have the time to spare and want to save some dough, opt for a pre-mix. If you are looking to get rid of some serious rust damage, you should use a more powerful chemical.

Storage Container

It might not seem like a huge feature, but the container that holds onto your radiator flush plays a big role when it comes to efficiency. Especially if the flush will work more than once, the container must be thoroughly sealed to prevent exposure to air and avoid evaporation. Because the chemical reacts with metal, you will only find them in plastic containers. Opaque plastic is the best choice since light can impact chemical potency. If your flush comes in a clear container, it will lose some power every time it sees the sun. Use it soon after purchase to avoid any issues. 

Other Considerations

  • How long it takes. Think about how much time you’ll need to spend flushing your radiator. The more damage and build-up you’re facing, the longer it will take to get the job done. You can speed this up with a more potent solution used in conjunction with a pressure flush. If there’s not much damage, time won’t carry as much weight when considering your radiator flush options. 
  • Protection benefits. The more comprehensive the radiator flush, the longer the effects will last. Take a look at the extra benefits you can get from the solution, including removal of grease, deposits of oil, and rusted metal. Thorough cleaning will improve engine efficiency and let you flush the radiator less frequently. 
  • Vehicle compatibility. Make sure you can use your radiator flush with your vehicle. Consider the type of materials used in your radiator. Some flushes won’t work with nickel and can result in hardware damage. Others are more inert and won’t harm your radiator. Check your owners’ manual or look online to find out what your radiator system is made of, and make sure you pick a compatible flush. 
  • Environmental safety. Consider the practical aspects of the radiator flush. The chemical will drain out of your system, and it has to go somewhere. Eco-friendly solutions are safe on waterways and not prone to damaging flora. Otherwise, you’d have to contain the flushed fluid and dispose of it separately. 
  • Personal safety. Mixing chemicals can sometimes lead to spills. Because of the acidic nature of the radiator flush, be sure that you have a well-ventilated space, long sleeves, gloves, and goggles. Take a look at the active chemical used in the flush, and make sure you have a buffering agent to render it inert. Basic chemicals (like baking soda) help with acid burns while acids (like vinegar) counteract basic solutions.

Best Radiator Flushes Reviews & Recommendations 2021

Best Overall
Hy-Per Lube HFL400 Radiator Cleaner

This radiator flush comes in a 16-ounce container, meant to provide a single flush on any vehicle with a 15-liter system. The affordable formula is crafted to address all types of radiator buildup. Using a buffering agent to neutralize acids in your cooling setup, this formula can remove all kinds of debris. It descales any deposit, whether it is water-soluble or not. After you flush out the radiator, the result is a smooth-running system that isn’t prone to overheating. Since it’s so powerful, this flush requires only occasional use. Cost-effective and crafted to avoid damage to your vehicle’s hardware, this is a worthy pick. 


The only issue with this radiator flush is that it comes in a clear container, but if you store it in a cool, dark spot, there should be no issue. However, as with any chemical, if exposed to the sunlight, the formula can lose potency.

Best Value
Prestone AS107 Radiator Flush and Cleaner

It’s no surprise that the Prestone AS107 Radiator Flush and Cleaner makes our list. It comes in a 22-ounce container, letting you pour it in directly without watering it down. From there, it uses chelation to attach to rusted metal pieces and deposits of corrosion. Backed with natural fluid pressure, it flushes out the debris to leave you with a completely clean and functional radiator. It stands out for the ability to work with vehicles that have severe damage from rust. Excellent for cars with high mileage and those who drive a lot in hot weather, this radiator flush is a powerful value option. 


One thing to note is that although the chemicals used in this solution offer excellent rust removal since it relies on chelation, oil deposits won’t slip off as easily. 

Premium Pick
PrimoChill Radiator Cleaning Treatment

Because this radiator flush is built as a concentrate, you can adjust the amount used depending on the level of damage and build-up. Able to flush out your radiator efficiently, most applications require only half of the contents, diluted by distilled water. The pure water ensures that there are no heavy metals or small particulates disturbing the formula, letting the flush focus exclusively on the radiator itself. Users report that this rinse is effective on new and used vehicles alike. It visibly removes rust and corrosion debris. This radiator cleaning treatment can keep your car’s engine temperature stable and help the whole vehicle run more smoothly with lasting effects.


Keep in mind that this chemical is made specifically for radiators (hardware free of nickel). If the formula encounters this raw element, it will damage the surface—stick to using this treatment on radiators, and you’ll be just fine. 

Most Eco-Friendly
Radiator Genie Cleaning System

Unlike other options that rely on chemicals, this radiator cleaner uses water pressure and directed airflow to keep the radiator humming. It comes with two user-friendly cleaning wands. Both feature ergonomic grips and long tubes that let you reach difficult spots. Eliminating the risk of chemical damage due to overusing flushing agents, these cleaners blast away debris while leaving the hardware untouched. Plus, unlike other cleaners, you can use them on all parts of your ride. 


These water-pressure and air-blasters should be used in conjunction with an occasional flush. Their main virtue is that they are entirely eco-friendly, eliminate risk to your hardware, and can be used as often as you desire.

Most Powerful
Gunk Radiator Flush

Safe to use on all types of metal, the Gunk Radiator Flush is a worthy candidate for vehicles with advanced damage. It is explicitly crafted to improve the effectiveness of antifreeze and coolant, letting your engine stay at optimal temperature. Coming in a 22-ounce container, this powerful formula can eliminate rust and corrosion damage. While it does not specifically address oily residue issues, the flushing of rusted debris takes a lot of this particulate along. With specific instructions for use and enough flush solution to work on vehicles of all sizes, this is a good pick if you've noticed radiator issues. The formula takes limited rinsing to get the full effects and lasts over a long period. 


Keep in mind that this flush's formula is a serious skin irritant, but as long as you use safety gloves and goggles, the strong chemical gets the job done well.

Honorable Mention
Design Engineering Radiator Additive

Unlike standard flushes, this formula is an additive. Since your radiator cycles continually, it takes the idea behind a flush and lets you address issues while driving. The 16-ounce container goes into the radiator and uses a catalyzing agent to facilitate warm-up time for your engine, saving you half the time of warming the vehicle in cold conditions. You can use it with any kind of antifreeze because the solution is free of glycol. By increasing the efficiency of heat transfer from the engine to the heater, it accelerates the performance of the radiator itself. This results in less build-up over time, especially in terms of oil and grease deposits. 


One thing to note is that this is not technically a flush, rather something to use in conjunction with routine maintenance. It can drastically improve vehicle efficiency and limit how often you need to do a flush when used regularly.

Honorable Mention
BlueDevil Radiator Flush

Meant to extend the life of your vehicle, the BlueDevil Radiator Flush is a powerful solution for all types of automobiles. The chemical formula is made specifically to eliminate issues with grease and buildup. Naturally accruing with the use of the engine, these caked-on particles are a part of normal wear and tear on your ride. This flush is made to offer a deep clean, eliminating all types of debris and restoring the thermoregulation in your engine. Consumer reports highlight its continued effectiveness and ease of use. Whether used as a prophylactic when you purchase a pre-owned vehicle or as preventative maintenance for your ride, it is a terrific radiator solution. 


Although this chemical is powerful, it is not necessarily good for the environment. As a result, it’s better to put your car on a jack and run the engine from there. This way, it doesn’t leak onto the road

Tips

  • Be responsible with your radiator flush since most aren’t very eco-friendly. Avoid protected wilderness areas and waterways used for swimming or drinking. When possible, contain and dispose of the flush solution. 
  • Always wear personal protective equipment (PPE) when doing a radiator flush. The formula uses corrosives and can’t contact skin or eyes — or be inhaled. Wear goggles, long sleeves, and do the flush in a ventilated area. 
  • Only use radiator flushes on radiators, especially if the formula is nickel sensitive. The active agent in radiator flush is built to work with metals like aluminum. Don’t apply it to other parts of your vehicle (even if they are rusty). 
  • Radiator care is a critical part of preventative maintenance. Check its status occasionally and, when you perform a radiator flush, keep a record of it. 
  • Radiator flush can void some warranties. If a protection plan covers your vehicle, check the underwriting before you tackle this project.
  • Take your time when cleaning out your radiator. Properly executed radiator flushes can save you big down the line. Be sure to set aside enough time to do it right, lest you cause more damage to the system. 
  • Less can be more. Inherently, corrosives wear away at the metal. If you over-flush your radiator, it can damage the hardware. Should the chemical not work well enough, try blasting it with water. If the problems continue, consult a mechanic. 
  • Restore coolant levels after you flush out the radiator. Essential to proper function, it prevents you from damaging the radiator after stressing it out with cleaning. Always check your vehicle’s fluids as a part of routine maintenance. 

FAQs

Q: Are radiator flushes necessary?

Yes, radiator flushes are essential. They are an inexpensive way to improve your vehicle performance. It rids the system of dirt, rust, and grime that builds up naturally over time. This debris can block up the radiator and compromise performance. Regular radiator flushes protect the heat-transfer system in your ride. 

Q: When should you flush your radiator?

Some say you only need a radiator flush every five years or 100,000 miles. However, the more strain on the radiator, the more frequently you must clean it. Driving in hot environments or warming your engine in freezing temperatures, as well as frequent ascents and descents, causes radiator wear. More frequent flushes improve overall vehicle efficiency. 

Q: How long can I drive with a radiator flush? 

The minimum amount of time to run your engine with the flush is 10 minutes. That said, if you can, let the vehicle go for between three and six hours. Longer use allows it to more thoroughly flush out the system. Keep in mind that if the chemical solution is harsh, it can cause damage to the road. Sometimes, it’s better to idle the engine on jacks, especially if you’re in a state with heavy environmental protection laws. 

Q: How much should a radiator flush cost? 

If you’re going to a professional mechanic, you can expect to pay up to $150. However, if you do the work on your own, you can complete the flush for less than $50. Bear in mind that it is time-consuming, so be sure to schedule in a few hours to ensure the job is done right.

Q: How will I know if the engine flush worked?

Once you have flushed your radiator, you should be able to tell if the clean water you are pumping through the system is coming out clear or muddled. If it is clear, it is a sign that the flush worked and there is no longer a blockage in your radiator, Otherwise, you may need to keep adding solution and flushing it out until there are no signs of debris.

Q: How long does it take to flush a radiator?

This will depend on the severity of the blockage and the strength of the solution. Typically, it is best to let a liquid solution sit in your system throughout the day as you drive your normal routes. Then, flushing the fluid should only take a few minutes. If you are using a more concentrated powder like the IronTite, you will want to pay close attention to the directions because leaving it in too long could cause damage.

Q: What else do I need to flush my radiator beside the cleaning solution?

You will also need water to flush the solution out of your radiator after you have given it enough time to work. This can be done by pouring water into your radiator, but the easiest and most effective way would be to use a garden hose.

Q: How do I know when my radiator needs to be flushed?

Depending on the car and how far you are driving, you should only need to flush your radiator once every year or two. However, if you notice your radiator seems to be working poorly or your vehicle frequently becomes overheated, it may be time to flush it.

Final Thoughts

Now that you know what to look for in a radiator flush, you can keep your engine running smoothly. Perhaps you’ll use the Hy-Per Lube HFL400 Radiator Cleaner for its powerful performance. Or, maybe you’ll opt for the affordability of Prestone AS107 Radiator Flush and Cleaner.