Best Penetrating Oils

Over time, parts such as bolts, fasteners, and more can rust or corrode, eventually becoming nearly impossible to loosen. Penetrating oil lubricates even the stiffest, most stuck-together metal surfaces so they glide easily over each other. This tool is essential in every mechanic’s arsenal for its extensive versatility, whether it’s in the shop or for a DIY project.

We’ve rounded up and reviewed the best penetrating oils to help make your next engine repair go smoothly. We’ll discuss the pros and cons of each oil and delve into what customers thought of each, plus explain the essential features of penetrating oils.

Whether it’s loosening rusted bolts or declogging a cluttered pipe, choosing the right penetrating oil is vital to your vehicle’s performance. Be sure to understand the different types of penetrating oils and what works best for your engine before deciding on any oil products.

Different Types Of Penetrating Oils

1. Synthetic: These do not contain petroleum or mineral oils. Although more expensive than other oils, synthetic penetrating oils are fire-resistant and can act as a superb coolant.
2. Straight: These are generally petroleum-based or vegetable oils that don’t contain water. These are used more frequently for metal surfaces where lubricity is more important than heat reduction.
3. Water-soluble: Unlike the first two oils, these have a high water content and can be diluted in water for low concentrations. Water-soluble oils are generally reserved for parts that can be easily corroded by harsh solvents in some synthetic and straight oils.

Benefits Of Penetrating Oil

• Lubrication: Many penetrating oils lubricate metal parts. This reduces friction and loosens stuck or tightly-wound nuts and bolts. Usually, this is only a temporary fix but sometimes it can be long-lasting.
• Corrosion-resistance: Penetrating oils are designed to prevent metal surfaces from corroding. Over time, corrosion can significantly weaken metal, and oils displace moisture that can eventually lead to rust.
• Cleaning agents: Most penetrating oils can remove adhesives, tar, and more from metal surfaces. They can dissolve debris so they can be wiped away using a light abrasive such as a cloth or wipe. The best oils should also act as a rust penetrant and have water solvent properties to prevent rust buildup.
• Noise reduction: When metal surfaces corrode, they can produce awfully loud creaking and squeaking noises. Since penetrating oil prevents them from rubbing against one another, an additional benefit is that they reduce noise.

1. Best Aerosol: Kano AeroKroil Penetrating Oil
2. Best Liquid: Liquid Wrench Penetrating Oil
3. Best Multi-Spray Option: WD-40 Multi-Use Spray
4. Best Rust Remover: B’laster PB Penetrating Catalyst
5. Best Straight Oil: Gasoila Free All Deep Penetrating Oil

Kano AeroKroil attacks corrosion to free bolts, nuts, and other mechanical parts from scraping. Its advanced formula prevents rust and carbon deposits from forming to create a long-lasting protective coat that keeps your engine properly lubricated.

Due to its aerosol can design, AeroKroil penetrates deeper into metal than liquid oils and is faster-acting, as well. This product works on rubber and plastic, so it won’t damage them if spilled in your engine.

What Customers Are Saying

Amazon Review Score: 4.9 out of 5 based on over 2,000 ratings

Those who left positive reviews enthusiastically endorse the AeroKroil for how quickly it works after the first coat. Some customers note that a small amount of AeroKroil is enough to make a big impact on their engine.

While this product has mostly positive reviews, a couple of unsatisfied customers claim the AeroKroil did not loosen stuck bolts as well as they had hoped.

Having been in the automotive oil industry since 1941, Liquid Wrench is a tried-and-true name with more experience than most brands. Their penetrating oil works on rusted nuts and bolts and can even remove excess adhesive from stickers or other glues.

Liquid Wrench can seep easily between corroded metals thanks to its low surface tension. It’s safe to use on painted surfaces, and it contains no volatile organic compounds (VOCs), improving its everyday use. The only drawback of this oil is that it comes in a relatively small canister, so one bottle must be used sparingly.

What Customers Are Saying

Amazon Review Score: 4.6 out of 5 based on over 200 ratings

Many customers appreciate the speed at which Liquid Wrench worked, citing less squeaky hinges and clean parts within a few minutes of using it. There are also customers who like using the squeeze bottle for more precise application.

There are very few negative reviews on Amazon for this product, but some express dissatisfaction with the Liquid Wrench bottle, saying the spout broke after a few uses.

Another trusted name, WD-40 can unstick most stuck nuts and bolts. Its formula acts as a corrosion inhibitor to block moisture and other damaging elements to prevent rust. Also, WD-40 doesn’t contain any silicone, kerosene, water, graphite, or chlorofluorocarbons (CFCs), so it’s healthier for both your engine and the environment.

With WD-40’s Smart Straw, automotive enthusiasts can choose between a wide spray for broad application or a direct stream better for precise lubricating. And as a multi-purpose oil, WD-40 can be used on almost any sticky or squeaky surface.

What Customers Are Saying

Amazon Review Score: 4.7 out of 5 based on over 500 ratings

A majority of customer reviews recommend WD-40 spray as a must-have for both automotive and household use. There are also numerous reviews praising this product for how well it works on door hinges.

On the other hand, some customers found the Smart Straw ineffective for getting into hard-to-reach places.

B’laster PB Penetrating Catalyst has a non-evaporating formula that leaves behind a layer of protection against rust. Because of its low viscosity, this oil can reach between tight crevices with ease to break down corroded or rusted engine pieces.

Beyond cars, this penetrating oil also works on industrial, marine, plumbing, and other equipment. PB B’laster oil loosens frozen parts, which makes it ideal for quick fixes in cold weather areas.

What Customers Are Saying

Amazon Review Score: 4.7 out of 5 based on over 600 ratings

Some customers recommend allowing the PB B’laster to sit for a few hours to a day before wiping to obtain the best results against rust. Others believe that warming up parts and then spraying improves its performance.

Negative reviews say the PB B’laster’s spray straw clogs easily. However, more than eighty percent of reviewers left 5-star ratings for this penetrating oil.

Gasoila Free All Deep Penetrating Oil targets rust, corrosion, and adhesives with pinpoint accuracy. Its penetrating fluid can unstick screws, nuts, bolts, and clamps as well as moving parts such as universal joints and locks.

This oil contains no silicone additives, so it won’t damage any paint it may come in contact with. It doesn’t dry quickly, either, so only one or two coats and patience are required to watch the Gasoila go to work.

What Customers Are Saying

Amazon Review Score: 4.6 out of 5 based on over 3,000 ratings

Those who admired the Gasolia had positive things to say about how quickly it worked. Some reviewers mentioned that it works especially well for loosening grinding gears.

While many positive reviews said the Gasoila worked quickly, there were negative reviews that claimed the opposite, citing wait times of up to a few hours before seeing results.

To select the five penetrating oils in this review, our team searched retailers like Amazon, RealTruck, and Advance Auto Parts for top products, looking at factors such as customer ratings, prices, superlatives, and Prime shipping eligibility.

Why You Can Trust Us

Each year, we review over 1,000 auto products. Our team of product experts thoroughly researches top products and tests items on real vehicles when possible before making our recommendations.

We publish hundreds of product and service reviews to bring car enthusiasts detailed guides on automotive tools, detailing kits, car seats, pet products, and much more. For more information on our testing methodology and how we evaluate every product, check out our methodology page here.

Penetrating oil works to loosen the toughest car parts, including bolts and fasteners, by lubricating the area to make car maintenance or quick fixes easier for you. Every mechanic needs a penetrating oil to work on a vehicle or complete a DIY project from your own garage. This guide gives you all the important information you need when looking to buy the right penetrating oil for you and your vehicle.

*Data accurate at time of publication.