LAST UPDATED: June 23, 2019
Best Penetrating Oils: Loosen Jammed Bolts and Fight Rust
Loosen corroded bolts, stuck nuts, jammed pipes, rusted screws, and other stuck parts with our top picks for the best penetrating oil
The Review Team
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PUBLISHED ON June 23, 2019
If you have ever tried to turn a bolt that won't budge, then you will appreciate what penetrating oil does. Apart from eliminating the rust on a bolt’s threads, penetrating oil can clean and stop corrosion in tight places. It's a must-have item in every toolbox. Our detailed review provides a buying guide on choosing the best penetrating oil for rusted nuts.
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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.
Benefits of Penetrating Oil
- Lubrication. Most penetrating oils will offer temporary, if not long-lasting (some products have additives in their formula to increase the lubrication effect) lubrication to mechanical parts. The oil will help with reducing friction and will loosen frozen parts or tight bolts and nuts.
- Cleaning agents. Most penetrating oils can also be used as cleaning agents. They can effectively remove tars, greases, rust, and adhesives. The fluid will work as a solvent and will melt contaminants to a point where they are easy to remove using a tack cloth, a wipe, or a light abrasive.
- Corrosion-resistance. Penetrating oils are created to protect metal surfaces from corrosion. Corrosion is the biggest enemy of metals used in constructing mechanical parts. The oil has a formula that works by displacing moisture, which is a big part of the elements that cause rust and lead to corrosion.
- Noise reduction. Penetrating oils help to reduce rust and friction that often leads to squeaky door hinges, windshield wipers, a noisy suspension, screeching bike chain, and other noisy movable parts.
Types of Penetrating Oil
Water-Soluble or Emulsion Penetrating Oil
Water-soluble penetrating fluids have a high water content in their formula. They can also be diluted in water to get a concentration that’s lower than 10 percent. These oil types are best used for materials that can be damaged by highly-concentrated solvents with harsh chemicals in their formulation.
Synthetic or Semi-Synthetic Penetrating Oil
Synthetic penetrating oils are created from synthetic or semi-synthetic compounds such as polyglycol, silicone, diesters, esters, or a combination of water and synthetic fluids. These penetrating oils are more expensive than other products in this industry. However, synthetic oils are fire-resistant and great coolants.
The products under this type are made from base minerals and petroleum oils. The products do not need any dilution to be used and may contain other lubricants such as esters, fats, and vegetable oils. In some cases, the oils will also have other additives such as phosphorus, chlorine, and sulfur, and are great for machine parts lubrication.
WD-40 (Water Displacement-40) is a penetrating oil and water-displacing spray manufacturer based in San Diego, Calif. The company was founded in 1953 and has been providing penetrating fluids under the trademark name WD-40 since then. One of its best penetrating oils for seized bolts is the WD-40 Multi-Use Product.
Kano, officially known as Kano Laboratories, headquartered in Nashville, Tenn., is a company that focuses on producing specialty chemicals. The company boasts of selling its products to 480 of the Fortune 500 companies around the world. The Kano KROIL Penetrating Oil is one of the best rust penetrating sprays under the Kroil name and has been in the market since 1939.
B’laster Corporation is a company that manufactures and distributes B’laster lubricants, rust inhibitors, penetrants, and other specialty fluids for industrial and automotive industries. The company was founded in 1957 and is currently headquartered in Ohio. This company offers some of the best penetrating fluids for stuck bolts and the B'laster Penetrating Catalyst is one of them.
Best Penetrating Oil Pricing
- Under $20: This price level is for the basic-level penetrating oils that are mostly the water-soluble type. Most won’t have a long-lasting lubrication effect but expect to find some of the best rust penetrants in the market.
- $20 to $40: This mid-range price level holds a variety of high-end penetrants that offer both rust-preventive and water repulsion features, to subpar products with the least impressive features. The penetrants here could be either straight-oil or water-soluble products.
- Over $40: You will find high-end products here. Some of these oils in this category are similar to the ones in the cheaper categories only that they are offered in packs or in larger cans. However, most are synthetic and semi-synthetic penetrating oils.
Lubricity and Viscosity
Lubricity refers to the ability of the oil to reduce wear and friction in moving parts. If you intend to use the product on mechanical parts, you should focus on penetrating oil with a longer-lasting lubricating action. Viscosity is the measure of internal friction of the fluid and ranges from thick to thin. A low viscosity product will penetrate tight spaces faster and will go deeper with only a few drops.
Penetrating oils have varying temperature tolerance levels. Always check on the temperature tolerance on penetrating oils since you might need to use them on hot surfaces. Choose synthetic penetrating oil products for hot parts, as they also act as coolants.
The ingredients used to make the penetrating oil will determine how and where you can use the product. For instance, there are ingredients that will damage items made of rubber and plastic. There are also products that have extra additives for better performance.
- Quantity: When buying penetrating oil, make sure you look at the capacity of the products you are interested in and compare with others in the same price range. Always go for larger cans if you intend to use a lot of oil. Also, choose products with no expiration date if you are going for larger quantities.
- Convenience: A spray can that allows you to deliver a stream or a spray is the best option when it comes to convenience. Spray cans are easier to use and will deliver the oil faster and effectively. There are products that come with a straw for precision spraying.
- Environmental-Friendly: You should at least ensure that you buy penetrating oils made of eco-friendly ingredients. These products will not only play a part in conserving the environment, but they are also safe to use. Consider zero ozone-depleting compounds that are odorless.
Best Penetrating Oil Reviews & Recommendations 2020
Whenever you’re dealing with mechanical parts or components, you need them to be clean in order to work efficiently. When parts are clean, every mechanical part works as it is meant to. If you are looking for a bio-solvent penetrating oil that will clean up parts and also ensure they are protected, it's the B’laster BLP16-PB. It has one outstanding feature: the ability to dissipate rust and corrosion on metal parts.
Once you apply this oil, it will get rid of the rust and the corrosion. Like the best penetrating oils, it can penetrate very small openings for an effective clean. The oil is specially designed to loosen bolts and nuts that are extremely hard to open. However, the amount of time it takes to loosen parts will depend on the rust and corrosion buildup. On average, it doesn't take more than a couple of minutes. And since it is sprayable, it is a lot easier to apply.
This penetrant has a nozzle with a small opening that ensures none of the product is wasted. You only need to spray a small amount for it to work. However, the fumes it produces when applied can be a little overwhelming, so avoid using it indoors. The can is also not very well-constructed and may shatter on impact when you drop it on the floor.
Developed in 1894, this multipurpose drip oil is loved by many tradesmen and DIY enthusiasts. It lubricates and cleans parts and protects them against rust and corrosion. Its small nozzle makes for precise application and ensures there is no splatter or overspray. You can use it on small motors, sliding doors, wheels, casters, chains, bicycles, nuts, bolts, power tools, and many other moving parts. It is also a powerful tool for removing dirt and grime.
You can never go wrong with this multipurpose oil, as it can be used for a variety of tasks in both residential and commercial environments. At home, you can use it on door hinges, faucets, and fans. We love the fuel level indicator strip that allows you to see exactly how much oil is left. You will also appreciate the fact that it comes in two sizes: 3 ounces and 8 ounces.
However, we have a few negative comments about this oil. For starters, the new can is not very user-friendly and does not dispense oil as it should. The oil pours out of the spout instead of coming out in drops. The cap is also fixed very tightly and is difficult to open. You'll have to use some force, which may cause the oil to gush out.
One of the things we love most about the Kano KROIL Penetrating Oil is its ability to penetrate extremely small spaces. It can penetrate spaces so small they can't be seen by the human eye—like one millionth of an inch. It is one of the best oils for rusted components and you only need to use a little of it to see results. The oil loosens rusted or frozen nuts and bolts in a couple of minutes. It was developed by chemical engineers and is highly versatile. It not only works on mechanical parts, but it can also be used on electrical parts.
This penetrating oil can stop squeaks, loosen joints, prevent corrosion, and displace humidity and moisture (which are the main causes of rust). And since it has low viscosity, it easily creeps into confined spaces to do its best work. We also love the fact that it doesn't dissolve quickly and continues to lubricate parts a while after it has been applied. It does not damage the molecular structure of an object and can be used on aluminum and brass.
However, we are not too happy about its price, which puts it out of reach for many people. The container also bends easily and is not of the highest quality. And since it doesn't have a small nozzle, you may use more of the product and buy a new one sooner than you expected.
Liquid Wrench is a family-owned company that's been operating since 1941. The penetrating oils, lubricants, and greases the company manufactures help industrial and automotive professionals to solve all types of problems, from everyday ones to extraordinary ones. The Liquid Wrench L104 quickly dissolves rust and cuts through grease. You can use it to free any stuck bolts, nuts, and locks.
Whether you need to clean the residue of adhesive stickers or free mechanical parts from rust, this penetrant will do a great job. It has the ability to penetrate into the tiny spaces where threads of rusted parts meet. It has low surface tension which allows it to easily creep into rusted parts. The penetrant does not have a bad odor and is safe to use on painted surfaces. It also contains no volatile organic compounds (VOCs).
Before you use this penetrating oil, shake it well, then spray it liberally on the rusted parts. A few drops will go a long way. However, it comes in a small 4-ounce can and may not be sufficient for you if you’re a professional who spends a lot of time dealing with rusted parts and components. And compared to other penetrating oils of the same size, it is more expensive.
This penetrating catalyst is sold in a pack of two, so you can use it for longer. It is specially designed to penetrate and loosen rusted or frozen metal parts. It has been on the market since 1957 and is loved by many professionals and DIYers. Its non-evaporating lubricant reduces friction between surfaces and prevents further rust and corrosion.
Don't let rust and corrosion spoil your tools and equipment. With this penetrating catalyst, you can salvage rusted parts, lubricate squeaky and stuck machinery, and prevent further corrosion.
What you will love about this penetrating catalyst is that it can be used on a variety of objects, from rusted nuts to brake calipers. The oil quickly breaks rust bonds and loosens frozen metal parts. It can be used on cars, boats, and industrial parts. Some plumbers also use it in place of plumber’s grease. It can easily lubricate a kitchen faucet that's stuck.
However, it’s worth noting that the oil has an overpowering smell. It’s best to apply it after opening your home’s doors and windows. Also, the amount of lubrication it offers is not as good as what the best penetrants offer. Applying the product on small parts is also difficult because the can does not come with a straw.
One of the things we love about WD-40 is its commitment to putting customers first. Its rust-release penetrant spray is compliant with the state regulations regarding volatile organic compounds in all 50 states. This means you don't have to worry about the effect of VOCs on your health as you use it. The penetrant frees rusted and stuck-together parts and leaves a protective layer to prevent more rust and corrosion.
This rust-release penetrant lubricant spray is a rust buster and water displacer. This is a water-soluble oil that can attack the water particles found in mechanical parts. It will also remove dirt and grime. It quickly dissolves after application, so you won't have to deal with a lot of oil as you work and make a mess. You can apply it in two ways: When you want to apply it in specific areas, use the straw; when you want to apply it on larger areas, flip the straw down.
However, unlike other lubricants, it is hygroscopic (it absorbs moisture from the air). This means you shouldn't use it as a daily alternative to general lubricants. It also dissolves very fast and its straw is not very easy to use. You may also find it difficult to get the last bit of the product out of the container.
One of the things most people consider when buying a penetrating oil is the viscosity. Viscosity measures the internal friction of a fluid. It also refers to how easily oil pours at a specific temperature. Oil that is very thick may have a lot of surface resistance and may not creep into parts and components as rapidly as you would want.
The B'laster PB Penetrating Lubricant has low viscosity and easily penetrates into parts without any issues. It can be used on marine instruments, automotive parts, industrial machinery, and other equipment. If you are a plumber, you can use it to loosen faucets and other plumbing fittings.
This penetrating lubricant is sold in a pack of three, so you will get value for your money. After applying it, it leaves behind a lubricating film to prevent rusting and corrosion in the future. But you may not like the odor it leaves behind. The can may also run out of pressure before the product is finished. And you have to be careful when using the can; it may get dented or shatter if you happen to drop it.
Liquid Wrench is a family-owned company based in Charlotte, North Carolina. It has been developing products for more than 75 years and its commitment to innovation and quality has earned it the trust of both tradesman and avid DIYers. So, if you are in the market for a penetrating oil that can cut through grease and quickly dissolve rust, the L116 may be the answer to your needs. You can use it on bolts, hinges, rusted nuts, pipe fittings, clamps, locks, latches, and much more.
The L116 Liquid Wrench Penetrating Oil is also ideal for frozen parts and hose pipe fittings. It does not have a powerful odor that overwhelms and contains no volatile organic compounds. It’s rare to find a penetrating oil that is gentle on plastic and PVC, but this one is. You can also use it on painted surfaces and it won't damage them. It is a fast-acting, anti-seize formula with low surface tension, low viscosity, high solvency, and high lubricity. It easily cuts through the toughest of rust.
Knowing which penetrating oil to use is key to having great results. The L116 has all the features that experts look for in penetrating oil.
However, you may not like its smell, which lingers after application. Its nozzle is also not very well-built and may break after a short period.
- If you are dealing with a stuck bolt that won’t come loose even after using the penetrant, use a heat gun to warm up the bolt and it will automatically expand. You can then wrench it out. However, make sure the penetrant has a high heat tolerance, or keep the heat at a moderate temperature. Do not ignite the bolt if you used a petroleum-based oil to loosen it.
- If you need to use the penetrating oil often, go for larger quantities. Most people do not realize that penetrating oil is available in large quantities because most brands only market smaller cans.
- If the penetrating oil container does not come with a precision straw, you can always get an aftermarket option. There are precision applicators sold separately and will help you deliver the oil in tight spaces. You can also convert a syringe and needle into a precision applicator.
Q: How long does it take for penetrating oil to take effect?
A: In most cases, you will have to wait for about 15 minutes for the oil to work effectively. It will, however, depend on the quality of oil and what it’s penetrating. Some penetrants will even need a whole hour and some wrenching to get the nuts loose. Using precision applicators can however reduce the action time.
Q: Does penetrating oil provide lubrication?
A: Yes. Most penetrating oil products provide some kind of lubrication. The problem is that the lubrication will not last long and you may have to use other lubricants. There are, however, penetrants with more lubrication properties than others.
Q: Are penetrating oil products flammable?
A: A good number of penetrating oil products have low flash points that lead to high flammability. This means that the products cannot be used on hot or fiery surfaces. However, there are some products that have high-temperature tolerance and can remain stable in high-temperatures surfaces like an engine.
Q: Can the penetrating oil be used on aluminum parts?
A: Unless specified, most penetrating oils will work well with all metals. You can effectively apply the oil on seized aluminum parts and get great results. It is always important to check on the instructions from the manufacturers to see on which surfaces the oil can or cannot be used.
We’ve chosen the B'laster BLP16-PB 12 oz. Penetrant as the best penetrating oil. It works on a variety of components and does not harden or lose its penetrating ability.
Our choice for the best value penetrating oil is the 3-IN-ONE 10038 Multi-Purpose Oil. It’s a hard-working spray that penetrates deeply and quickly.