The 10 Best Penetrating Oils

Splurge on the best penetrating oil you can afford so that rusted or seized nuts and bolts don’t cause you trouble.

Penetrating fluids do more than just eliminate rust on stubborn parts. They can also be used as a lubricant, metal cleaner, corrosion stopper, adhesive remover, and much more.

This review catalog and buying guide highlight the best penetrating oils on the market so that you can find the right one for your car, truck, motorcycle, RV, or any other piece of equipment that needs oiling. Here’s a quick rundown of our top 5 picks:

Best Penetrating Oil Reviews

We considered the following factors in selecting each penetrating oil. Get more details about them and several others in the buying guide section:

• Ingredients: We assessed the quality, effectiveness, and safety of their ingredients.
• Lubricity: We looked at the capacity of the penetrating oil to reduce friction and/or wear. 
• Viscosity: How thick is the oil and how easily does it flow? Low viscosity penetrating oils typically penetrate deeper and faster into tight spaces than higher viscosity ones.
• Heat tolerance: Some oils handle heat or cold better than others. The better a penetrating oil can tolerate extreme temperatures, the more versatile it is.
• Ease of use: The penetrating oil should be easy and unmessy to use.

1. Kano Aerokroil Penetrating Oil 

The Kano Aerokroil Penetrating Oil is a popular choice for a whole host of applications in the garage, workshop, or around the house.

Widely considered a “jack-of-all-trades, this multi-purpose oil has a low viscosity that allows it to penetrate up to a millionth of an inch, creeping into the tiniest of spaces to displace water, provide lubrication, remove rust, prevent corrosion, and clean surfaces.

Its triple-action formula can loosen the stubbornest fastener quicker than most other penetrating fluids.

Not only can it be used on cars, mowers, tractors, guns, and virtually any machine part, but you can also use it to dissolve dried oil, grease, and gum.

The Kano Aerokroil comes in a spray bottle, making it easy to apply and helping ensure that you don’t use more of the product than necessary.

One potential downside is that the formula contains petroleum oil, which can damage some materials.

Product Specs

• Application: Spray
• Quantity: 16.5 oz (488 ml)

Bottom Line

The Kano Aerokroil Penetrating Oil does a superb job at loosening rusted parts, stopping squeaks, preventing corrosion, and displacing moisture. CHECK LATEST PRICE

2. WD-40 Multi-Use Penetrating Oil

The iconic WD-40 Multi-Use Penetrating Oil has been used in many American households for decades — since 1953, in fact. It works on almost anything, from metals and plastics to wood and rubber.

This rust-busting, water-displacing solution is specifically optimized to attack the water particles that cause corrosion. Not only does it free rusted and stuck-together mechanical parts, but it also creates a protective barrier that protects them against more rust and corrosion.

The WD-40 Multi-Use Penetrating Oil is also an effective cleaning agent capable of removing dirt and grime, and compliance with government regulations regarding volatile organic compounds makes it safe to use.

It can be applied in two ways: Use the straw when you need precision, and flip the straw down when you want to target a larger area.

Unfortunately, WD-40 is hygroscopic and dissolves very fast, making it not suitable as a lubricant.

Product Specs

• Application: Spray
• Quantity: 8 oz (237 ml)

Bottom Line

The WD-40 Multi-Use Penetrating Oil is so popular and revered that it has almost become synonymous with ‘penetrating oil’. CHECK LATEST PRICE

3. 3-IN-ONE Multi-Purpose Oil

Developed in 1894, the 3-in-1 Multipurpose Oil is the granddaddy of all the penetrating oils on our list. It’s a tried-and-test lubricant and cleaning agent that effectively removes rust and cleans and protects parts against rust and corrosion.

You can use it for both commercial and residential applications and on a wide variety of equipment, such as small motors, wheels, door hinges, power tools, faucets, bicycles, chains, and of course, fasteners like nuts and bolts.

Although some users may prefer a spray method of delivery, a squeeze bottle design improves precision and allows the oil to be applied with little to no overspray or splatter,

Unfortunately, the cap on the bottle is tightly fixed and can be hard to open. The force you will need to exert may cause some oil to gush out.

The 3-in-1 Multipurpose Oil is the oldest and lowest-priced product on our list of best penetrating oils, but certainly not the lowest quality.

Product Specs

• Application: Liquid
• Quantity: 8 oz (237 ml)

Bottom Line 

Despite being well over 100 years old, the 3-in-1 Multipurpose Oil remains one of the most loved penetrating oils on the market. safe to use. CHECK LATEST PRICE

4. Liquid Wrench Penetrating Oil

From freeing mechanical parts from rust to removing adhesive stickers, the Liquid Wrench L104 is a top-shelf penetrating oil that seems to do it all. It easily cuts through rust and grease as a high-quality oil should.

As a low viscosity, low surface tension formula, this solution easily penetrates tiny areas and creeps into rusted parts. It will loosen the stubbornest of stuck nuts, bolts, and locks.

The formula doesn’t contain volatile organic compounds, nor does it have a bad odor.

While all you need is a few drops to get the job done, the Liquid Wrench Penetrating Oil is sold in a small 4-ounce bottle that may be insufficient for your needs. Moreover, it’s more expensive than comparably-sized penetrating oils.

Product Specs

• Application: Liquid
• Quantity: 4 oz (118 ml)

Bottom Line 

A fast-acting, anti-seize formula allows the Liquid Wrench Penetrating Oil to dissolve oil and cut through grease with ease. CHECK LATEST PRICE

5. B’laster BLP16-PB Penetrating Oil

The B’laster BLP16-PB has been a best-seller since 1957 and is easily one of the best penetrating oils for the money.

Sold in packs of 12, this fast-acting formula quickly penetrates and saturates metal surfaces to break through rust and loosen rusted, warped, and frozen parts. It dissipates rust and corrosion before your very eyes.

The B’laster Penetrating Oil also acts as an effective cleaning agent and a non-evaporating lubricant that prevents rust and corrosion.

The solution comes in a spray bottle, making it easy to apply and ensuring that you don’t accidentally waste any.

One downside, however, is that the fumes it generates can be a bit overwhelming. Avoid using this penetrating oil indoors.

Product Specs

• Application: Spray
• Quantity: 11 oz (325 ml)

Bottom Line 

If you’re looking for a quality penetrating oil that effectively cleans metal parts and provides protection against rust and corrosion, the B’laster 16-PB has you covered. CHECK LATEST PRICE

6. Kano Kroil Penetrating Oil

The Kano Kroil Penetrating Oil is very similar to the higher-ranked Kano Aerokroil. However, instead of coming in a spray bottle, you get an old-school aerosol can.

Like the Aerokroil, it penetrates up to a millionth of an inch, creeping into tiny spaces to displace water, treat rust, and clean and lubricate the surface. It can loosen and free the stubbornest of nuts, bolts, and screws.

This penetrating fluid doesn’t expire and works on cars, bikes, tractors, mowers, guns, and just about any mechanical equipment with moving parts.

The fact that the solution doesn’t come in a spray bottle makes it a little harder to use than the Aerokroil, though, not to mention it contains petroleum oil, which is known to damage certain materials. 

Product Specs

• Application: Liquid
• Quantity: 8 oz (237 ml)

Bottom Line 

Not having an expiry date means you can use the Kano Kroil Penetrating Oil for a very long time. CHECK LATEST PRICE

7. Gasoila Free Rust Eater Penetrating Oil

The Gasoila Free Rust Eater Penetrating Oil does exactly what its name implies — it eats rust.

This formula is so effective at penetrating and dissolving rust, grease, scale, carbon, and graphite deposits that you might not even need a blowtorch and hammer to loosen those stubborn stuck nuts and bolts.

It’s also a versatile lubricant that works on a wide variety of equipment, such as bicycles, cranes, home appliances, air compressors, just you name it. Heck, use it to polish wheel guards if you want.

There’s no need to worry about your paint being damaged, seeing as there is no silicone in the formulation.

Widely considered Gasoila’s best penetrating oil, the Free Rust Eater is as easy-to-use as it is effective. Its spray bottle design lets you attach a straw for extra precision when needed.

Product Specs

• Application: Spray
• Quantity: 11 oz (325 ml)

Bottom Line

The Gasoila Free Rust Eater Penetrating Oil is true to its name — it eats rust with extreme prejudice. CHECK LATEST PRICE

8. CRC Knock’er Loose Penetrating Oil

Ridiculous name aside, the CRC Knock’er Loose Penetrating Oil is very unique in that it freezes the area on which it is applied, causing cracks that the oil then penetrates.

Despite not evaporating as fast as other penetrating oils, it works fast, taking less than 5 minutes to dissolve rust and loosen nuts, bolts, and screws.

Whatsmore, the Knock’er Loose comes in an aerosol can that makes it easy to apply. It’s also VOC compliant, having been certified for use in meat processing plants.

The CRC Knock’er Loose Penetrating Oil is temperature sensitive and shouldn’t be used on car engines or for other high-temperature applications due to the risk of fire.

Product Specs

• Application: Spray
• Quantity: 13 oz (385 ml)

Bottom Line 

If you’re trying to loosen a stuck, seized or frozen nut or bolt and conventional oils aren’t working, try the unconventional CRC Knock’er Loose Penetrating Oil. CHECK LATEST PRICE

9. Royal Purple Maxfilm Synthetic Penetrating Oil

The Royal Purple Maxfilm is a high-strength, deep penetrating synthetic oil spray that works particularly well on heavy-duty machinery. In fact, it’s the one to get if you have a seized engine.

Dubbed ‘synerlec technology’, this solution’s sophisticated formula penetrates deep into rusty and jammed parts of machinery and other constructs, loosening up nuts, bolts, pipes, hinges, etc. 

It also acts as a tapping fluid, a powerful lubricant, and a protective agent against rust and corrosion.

You can use it on most metal surfaces without causing stains or other issues. 

As a premium product, the Royal Purple Maxfilm Synthetic Penetrating Oil is fairly expensive. Good thing it’s very cost-efficient.

Product Specs

• Application: Spray
• Quantity: 11 oz (325 ml)

Bottom Line 

If nothing else, the Royal Purple Synthetic Penetrating Spray Lubricant does a spectacular job of protecting parts from rust and corrosion. CHECK LATEST PRICE

10. LA-CO Precision Spout Oiler Lubricating Oil

Chances are you’ve never heard of the LA-CO Precision Spout Oiler Lubricating Oil, but if it made our list, then you can bet it’s a worthwhile product.

This solution was formulated to access hard-to-reach areas that most other penetrating oils can’t access and comes packaged with a 13-inch long telescopic straw for precision applications.

In addition to being an excellent rust-remover, it can be used to lubricate engines, door hinges, vacuum bearings, HVAC, roller bearings, etc. 

The oil comes in a small bottle, but you don’t need a lot to get the job done. Your purchase can potentially last you a year or more.

The LA-CO Precision Spout Oiler can tolerate higher temperatures than most penetrating fluids; however, exposure to direct sunlight can cause the solution to unexpectedly spill out of the bottle.  

Product Specs

• Application: Liquid
• Quantity: 8 oz (237 ml)

Bottom Line 

If you want rust removal and lubrication on small, tight areas, the LA-CO precision oiler is a great all-around solution. CHECK LATEST PRICE

Penetrating Oil Buying Guide

This comprehensive buying guide provides a host of valuable facts, tips, and best practices for finding the best penetrating oil for any project.

Related: The 10 Best Chassis And Truck Frame Paints

What Is Penetrating Oil?

Also known as penetrating fluid, penetrating oil is a very low-viscosity oil that is used to loosen and free rusted mechanical parts (bolts, nuts, etc.) so that they can be removed.

How Does Penetrating Oil Work?

The low viscosity of these fluids allows them to easily penetrate the smallest cracks and spaces. Once the oil seeps in, it removes rust and lubricates the surfaces to improve surface tension.

The reduced friction loosens and frees the fastener or mechanical part being worked on, making it easier to remove.

What Is Penetrating Used For?

In addition to loosening seized bolts, nuts, and other fasteners, penetrating oils are sometimes used as a general-purpose lubricant, cleaner, and corrosion-stopper, though they are usually not optimized for such functions. They can even be used to remove chewing gum, stickers, and certain types of paint.

Basically, penetrating oils are suitable for various projects in the garage, workshop, or around the house.

4 Benefits Of Using Penetrating Oil

Penetrating oils offer several key benefits that make them a necessary addition to your equipment repair and maintenance toolbox.

1. Lubrication: Most penetrating oils are formulated to offer some form of temporary or long-lasting lubrication, helping reduce friction between machine parts and loosen stubborn nuts, bolts, hinges, etc.

2. Prevents rust, corrosion: Penetrating oils protect metals from rust and corrosion. They serve as a coating that protects against moisture, one of the biggest causes of rust and corrosion.

3. Cleans surfaces. The best penetrating fluids can also be used as effective cleaning agents that remove grease, tar, rust, adhesives, chewing gum, paint, and other undesirable substances. 

4. Noise reduction: The lubricating, rust-preventing, and friction-reducing properties of penetrating oils work together to quiet down noisy parts, such as noisy suspensions, windshield wipers, screeching bike chain, squeaky door hinges, etc.

Types Of Penetrating Oil

There are three main types of penetrating oil, each with unique advantages and disadvantages: straight oils, water-soluble or emulsion oils, and synthetic oils.

Straight Oil 

Straight oils are particularly great for lubricating machine parts. Made from petroleum oils and base minerals, they don’t need to be diluted to be usable.

Straight oils sometimes contain other lubricants such as vegetable oils, esters, and fats, as well as additives like sulfur, chlorine, or phosphorus. 

Water-soluble Or Emulsion Penetrating Oil

Water-soluble penetrating fluids contain a high level of water and can be further diluted in water to achieve concentration levels below 10%. 

Less flammable than straight oils, these types of penetrating oils are well-suited for materials that are prone to damage from solutions with high concentrations of harsh chemicals.

Synthetic Or Semi-synthetic Penetrating Oil

These types of penetrating oils are made from semi- or fully-synthetic compounds, the most common of which are silicone, polyglycol, esters, diesters. Some are formulated from a blend of synthetic fluids and water.  

Usually more expensive than straight and water-soluble oils, synthetic penetrating oils are fire-resistant and make for great coolants.

Top Penetrating Oil Brands

There are many penetrating oil brands on the markets, so much, in fact, that choosing the right penetrating fluid can be a challenge for some people. Fortunately, there are several reputable brands that you can always count on to deliver high-quality products.

WD-40

Founded in 1953 originally as the Rocket Chemical Company, the WD-40 Company is an American manufacturer of household and multi-use products known best by its signature brand, WD-40 (Water Displacement-40).

Their products are sold in over 176 countries around the world, including the very versatile WD-40 Multi-Use Product, which has long been a great penetrating oil for seized bolts.

WD-40 Company is also the owner of 3-In-One Oil, a brand lauded for its excellent Multi-Purpose Oil.

KANO

Kano Laboratories, or ‘KANO’ for short, is a company that specializes in producing lubricants and cleaner products. Such is the reputation of this company that its products are used by 480 of the world’s Fortune 500 companies. 

Developed in 1939, the highly-regarded Kano KROIL Penetrating Oil is among the best penetrating fluids for treating rusted nuts, bolts, and screws.

B’Laster

The B’laster Chemical Company was created in 1957 in response to the excessive amounts of rust forming on mining equipment at the time. The company has since grown to offer a wide selection of lubricants, penetrants, rust inhibitors, and other specialty fluids for both automotive and industrial applications.

The B’laster Penetrating Catalyst is one of the best-selling penetrating fluids on the market.

Penetrating Oil Pricing

Penetrating oils are fairly inexpensive products, but paying more typically gets you better quality and performance, more quantity, or both.

Budget

You will find a lot of basic penetrating oils for $20 or less, especially the water-soluble variety. Most don’t provide long-lasting lubrication.

But don’t be quick to dismiss the category entirely — some truly excellent penetrating fluids have remarkably low prices. Just don’t expect to get a large quantity to work with.

Mid-Range

These penetrating oils can cost anywhere from $20 to $40. You have a large selection of high-end penetrants to choose from, including straight oils. They typically have both water repulsion and rust-preventive properties. 

Premium

Penetrating oils costing over $40 tend to be high-end products, and most are either fully synthetic and semi-synthetic. However, some oils in the lower price brackets are also offered at such prices but in packs or larger containers.

Features Of The Best Penetrating Oil 

Having an understanding of the essential features of penetrating oils will improve your chances of finding the best one for your car, truck, or any other equipment that requires oiling. Let’s go over eight key factors you should consider when making a selection.

1. Oil Purpose

Before choosing a penetrating oil, you need to know what it will be used for. For instance, If your primary goal is to remove rust, you’ll want an oil with a strong anti-rust formula.

If you want something that’s also a good lubricant and cleaning agent, a multi-purpose penetrating oil would be more ideal.

Always bear in mind that some metal parts react adversely to certain types of penetrating oil. For instance, if you plan to use the oil on hot surfaces, you need one that is fire-resistant.

2. Lubricity, Viscosity

Lubricity refers to a penetrating oil’s ability to reduce friction and or wear. If you plan on using the oil on machine parts, we recommend getting one that provides long-lasting lubrication.

Viscosity, on the other hand, is the measure of a fluid’s thickness and flow. Low viscosity penetrating oils penetrate and travel deeper and faster into tight spaces than higher viscosity solutions.

3. Temperature Tolerance

Penetrating oils have varying levels of temperature tolerance, so always check for their temperature tolerance even if you don’t plan on using them on hot surfaces.

Synthetic penetrating oil fluids act as coolants, making them better suited for hot parts than other types of penetrating oils.

4. Product Formula

How a penetrating oil is used and where it can be used will largely depend on its ingredients. Even high-quality penetrating oils can contain additives that may be harmful to certain materials such as rubber and plastics.

Always check the ingredients to make sure they are well-suited for your needs.

5. Convenience

When it comes to convenience, nothing beats penetrating oils that are delivered via spray. Not only are spray cans easier to use, but they also deliver the oil faster and more effectively.

Products that come with a straw or tube offer the utmost precision, allowing you to easily treat small, hard-to-reach parts.

6. Quantity

Make sure to compare the capacity of the penetrating oil of interest to other oils in the same price range. It’s best to opt for bigger cans and bottles if you plan to use a large quantity of oil. 

Also, check the expiration date if there is one. If you require a large quantity of oil and plan on storing some over a long period, penetrating oil with a long expiration date would be ideal.

7. Environmental-Friendly 

It helps to buy a penetrating oil product that is backed by the necessary environmental agencies in your country. Not only do eco-friendly products play a part in protecting our environment, but they’re also usually safer to use.

Consider going with formulas that are odorless and don’t emit ozone-depleting compounds.

8. Price

Price strongly correlates with quality when it comes to penetrating oils, so don’t skimp if you can afford not to. Many highly-rated penetrating oils command a premium, especially fire-resistant synthetic and semi-synthetic formulas.

But that’s not to say low price equates to poor quality. On the contrary, most penetrating oils, including many of the top-rated ones, are affordable. 

How To Use Penetrating Oils

This section provides a step-by-step guide to using penetrating oil to free rusted, seized, or frozen fasteners (nuts, bolts, screws, etc.).

Things you’ll need:

• Safety goggles to protect your eyes
• A quality wire brush
• A wrench and hammer
• A nut splitter
• Small blowtorch or, preferably, an induction heater tool
• A good penetrating oil. 

Note: Don’t begin the process without first wearing safety goggles to shield your eyes from flying rust and metal debris.

Step 1: Scrub Surface

Before applying the penetrating oil, remove the rust off the surface using a wire brush. Remove as much rust as possible.

Step 2: Remove Residue

Take a hammer and tap the edges of the fastener to shake off any remaining rust residue. Hit the edges gently, not aggressively, to avoid damaging the fastener.

Step 3: Apply Heat

Use a small blowtorch or, even safer, an induction heater tool to heat the fastener for about a minute (this will expand the metal). Make sure to take all necessary precautions to avoid starting a fire.

Step 4: Cool & Spray

Give the fastener some time to cool down, and then apply the penetrating oil. Spray the surface until it is properly saturated with the fluid.

Step 5: Loosen Grip

With the fastener now saturated with the fluid, take your hammer and tap it again to loosen up the grip so that the oil penetrates more easily.

Step 6: Use a Wrench

Wait several minutes, and then use a  wrench to loosen the fastener. If it’s still too tight, tightening and loosening it again sometimes helps.

Using a tool extender or a special bolt extractor can also help. Just be careful not to break the nut or bolt head.

If you were unable to remove the bolt or nut, try giving it another go by repeating the process.

Penetrating Oil Alternatives

You can make your own penetrating oil that, in some ways, works just as well as some factory-made oils. The following are the best homemade penetrating oil solutions.

Automatic Transmission Fluid and Acetone Mix

As it turns out, mixing the same quantity of automatic transmission fluid (ATF) and acetone results in an effective penetrating oil substitute. In fact, mechanics have been using this homemade solution for decades.

To make some for yourself, simply add a 50/50 mixture of automatic transmission fluid and pure acetone in an empty spray bottle. 

The two solutions separate like oil and vinegar, so you’ll need to shake the bottle to get a workable blend.

Vegetable Oil and Acetone

When a team of engineers at Drexel University carried out side-by-side comparison tests of several vegetable oil mixtures, automatic transmission fluid, and WD-40, they found that a mixture of vegetable oil and 10 percent acetone works just as well as WD-40 to free rusted nuts and bolts.

Increasing the concentration of acetone up to 30 percent of the mixture made the solution more effective than WD-40. 

Unfortunately, this penetrating oil substitute isn’t an effective rust-remover, and acetone is highly toxic and flammable. Don’t even think about making or using it without first wearing protective gear like gloves and goggles, and keep it away from anything hot, especially fire.

Penetrating Oil FAQs

Want to learn more about penetrating oils? The answers to these frequently asked questions highlight what they do, how they work, how to use them effectively, and how you can find the best one for your projects.

How Long Does It Take For Good Penetrating Oil To Work?

Although penetrating oils vary in their properties, the best oils tend to take around 15 minutes to work, with some taking a shorter time. The time depends on the quality of the oil, as well as on the material it’s being used on.

Is Penetrating Oil Flammable?

Many penetrating oils have low flash points, making them highly flammable. Straight penetrating oils, for instance, tend to be flammable and should be kept away from hot or fiery surfaces.

Some penetrating oils have fire-resistant properties that allow them to remain stable in high-temperature conditions.

What Are The Key Ingredients Of Penetrating Oil?

Penetrating oils are made from an eclectic combination of chemicals that work together to achieve desired levels of viscosity, lubricity, and rust removal. Common ingredients include low viscosity natural paraffin oils and lower alcohols such as methanol mixed with isopropanol.

Compounds and polymers such as alkyl succinic acid, polymethacrylate, zine dialkyl thiophosphate, and tert-butyl-p-cresol may also be active ingredients.

Does Penetrating Oil Damage Plastic?

Although high-quality penetrating oils will not damage plastic materials in most applications, certain light plastics such as polyurethane can become damaged. Always check the product specifications to make sure the oil is safe to use on the material you’re working on.

Can I Use Penetrating Oil On Aluminum Parts?

Unless stated otherwise by the manufacturer, penetrating oils generally work well on aluminum surfaces. As with other types of metals, using them to treat seized aluminum parts can get you great results. 

Is WD-40 A Penetrating Oil?

WD-40, which stands for Water Displacement 40th Formula, is believed to have been created by chemist Norman Lawson in 1953, the result of his attempts to concoct a formula to protect missiles against rust and corrosion.

WD-40 has most, if not all, of the characteristics of a penetrating oil despite not necessarily being fashioned as one. As a water dispersant first and foremost, it’s a less effective lubricant and cleaning agent than conventional penetrating oils, but it makes for a very good rust-removing and prevention solution.

Conclusion

With so many great and not-so-great penetrating oils on the market, finding the right one for your needs can be difficult. We hope that our detailed buying guide and review catalog provided you with all the information you need to make an informed decision.

Due to its solid combination of effectiveness, versatility, and affordability, the Kano Aerokroil Penetrating Oil is our choice for the best penetrating oil. The iconic WD-40 Multi-Use Oil is also another great option, while the 3-in-One Multi-Purpose Oil is our value pick.