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
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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.
- Best OverallWD-40 Multi-Use ProductSummarySummaryA multipurpose 8-ounce penetrating oil with a permanently attached straw and a two-way spray. You get one formula that solves several problems such as freeing sticky mechanisms, rust protection, and moisture repulsion.ProsProsIt’s a multipurpose penetrating oil. Comes in an easy-to-use spray can. You get a spray straw for precision application.
Stops corrosion, eliminates moisture, lubricates, and penetrates tight areas. It’s a high-quality product from a reputable brand.ConsConsThe lubricating effect may not last as long as expected. It’s not good for all plastics. Softens car polish and waxes.
- Best ValueKano KROIL Penetrating OilSummarySummaryAn inexpensive penetrating oil that works great with painted surfaces, plastics, rubber, and metal. It does not expire nor harden with time.ProsProsGreat for direct application. Comes with a spout for precise application. Has no expiration date. Ideal for a wide range of equipment. Long-lasting rust penetrant.ConsConsThe formula has petroleum which can damage some materials. It’s a temporary lubricant.
- Honorable MentionB'laster Penetrating CatalystSummarySummaryA premium penetrating oil with a fast penetrating action that allows access to deep, tight areas. It protects against rust, corrosion, and loosens moving parts such as bolts.ProsProsEffectively penetrates tight spaces. Also provides lubrication for moving parts. Works effectively and fast. Offers protection against corrosion. Its unique capillary action fights and prevents rust and moisture from all angles.ConsConsHas a low flash point: 150 degrees Fahrenheit. You will not get a spray for precision application. Emits lots of fumes.
Why Trust Us
All of our reviews are based on market research, expert input, and practical experience with each product 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 2019
Best Overall: WD-40 Multi-Use Product
The WD-40 multi-purpose oil is our top pick due to its single formula with several different functions. Some include lubrication, rust removal and prevention, penetration, and freeing of sticky mechanisms. The product can also be used on electrical systems based on its ability to prevent and drive out moisture. Additionally, it is environmental-friendly from the ingredients to the packaging.
This product comes in an 8-ounce aerosol can with a smart straw for two methods of application. First off, you could flip up the straw to get a stream to cover a wider area, or flip down the straw to get a jet-like spray for precise application. Its multi-purpose formulation makes it suitable for a variety of tools and equipment. It also doesn’t contain kerosene, water, silicone, graphite, or chlorofluorocarbons (CFCs).
However, if you are in search of lubricating oil that offers longer-lasting lubrication properties, this may not be the best choice. The lubricating effect is short-lived. It’s also not suitable for some plastics like clear polystyrene plastic. You should also take extra caution when using the product as the oil softens car polishes and other detailing products on contact. Despite that, this oil can be used in seized engines, alloy wheels, bike chains, and all types of bolts and nuts.
Best Value: Kano KROIL Penetrating Oil
The Kano Kroil Penetrating oil is our pick for the best value product based on its premium rust preventive features and price tag. The product comes in an 8-ounce can and loosens metal joints in minutes. The oil has a low viscosity that penetrates tight spaces fast and loosens rusted bolts and frozen metal parts. The can have a different design from the common aerosol cans as it comes with a spout for precision application.
This oil doesn’t have an expiration date. Neither does it harden nor gum over a long period. It can be used on a wide range of materials such as painted surfaces, plastics, rubber, and metal. The product can dissolve dried grease, gum, and oil, and does not affect any metal it comes in contact with. It stops corrosion by displacing moisture on applied surfaces and is one of the best penetrating oils for carbon deposits.
You may want to check whether the surface you intend to use the penetrating oil on is affected by petroleum. The product contains petroleum, which is known to damage some materials. There are also other chemicals in the formula that can be toxic. You need to wear safety gloves and a gas mask when using the oil.
Honorable Mention: B'laster Penetrating Catalyst
The B’laster penetrating catalyst is a top penetrating oil product with quick penetrative action. It quickly reduces surface tension and maneuvers its way through hard-to-reach crevices due to its low viscosity. It then loosens frozen or rusted metal parts within a few minutes. That saves you a lot of time as you won’t have to drill or burn off bolts, nuts, or pipe threads to let them loose.
The oil leaves behind a non-evaporating film that helps protect the surface from further rust and corrosion, and makes it almost impossible to experience the same problem in the future. For that reason, the B’laster is an ideal product for jobs on a vehicle’s suspension system, brakes, or the exhaust.
This product has a low-temperature tolerance. It’s therefore not suitable for use on hot or fiery parts. You will not get a straw applicator, and you would have to purchase one separately. Also, the oil emits a lot of fumes when used, so it’s better to wear a gas mask to protect yourself. Despite the cons, the B’laster is a multipurpose product suitable for plumbing, industrial, marine, and automotive equipment.
- 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.
Our top pick for the best overall penetrating oil is the WD-40 Multi-Use Product. It has several uses on top of rust prevention and offers the convenience of a spray applicator.
If you are not looking to spend a lot of money, but need to get a high-quality penetrating oil, the Kano KROIL Penetrating Oil has a lot to offer.