Best Penetrating Oil

A Guide to The Best Penetrating Oil

Have you ever tried to remove a bolt or screw that was rusted in place? If so, chances are that you used some brand of penetrating oil to prevent having to take more drastic measures to remove that bolt.

Some bolts can be removed with nothing more than a squirt of vegetable oil. Other bolts are so rusted in place that it feels like you need dynamite!

Every homeowner and toolbox needs a little can of penetrating oil.

By the way, penetrating oils do expire. If that can you’ve had in your toolbox is more than a couple years old, it’s time to ditch it for a new can.

Penetrating oils displace water. What makes them so useful (not to mention what makes them go bad so quickly) is that they have volatile ingredients that evaporate.

Not to mention that penetrating oils collect dirt and dust that contaminate them, even when properly sealed.

Wondering what the best penetrating oil on the market is? I’ve taken some time to consider all the possibilities and I’ve found some interesting points you shouldn’t miss.

The Best Penetrating Oil

If you’ve hung around a few auto repair shops, chances are that you’ve seen someone pull out a can of Blaster to loosen tight bolts.

Blaster has been around for decades and they claim they are the best selling penetrating oil since 1957.

I don’t doubt it.

This penetrating oil states that it contains a non-evaporating lubricant. It’s there to prevent future rust and corrosion while loosening current rust and displacing water.

Blaster can be used on more than car parts. It works on motorcycles, firearms, sports equipment, fishing reels, boating equipment, even toys, or sewing machines.

Most users found that Blaster (commonly referred to as PB) worked amazingly well on nearly every application. There were a variety of suggested methods for removing frozen bolts and how Blaster could be used to its utmost advantage. Everything from using a wire brush first to using a metal pick to remove as much rust as possible from the threads.

A few users found that the fumes were a bit overwhelming in an enclosed space. Others said that they were not impressed with their results.

I like Blaster because I’ve used it for years and always had great success in my applications but try a can for yourself. You will probably be more impressed than you thought possible.

Our Runner Up

Known as “the oil that creeps”, Aerokroil is well known for its ability to reduce surface tension. That allows this solvent to literally “creep” into the tiniest opening. The company claims openings as tiny as one-millionth of an inch.

This is the aerosol version of the old favorite Kroil penetrating oil. Sometimes you need an aerosol when the object is difficult to reach or its depth and position make an oil awkward. A door lock cylinder comes to mind.

Aerokroil dissolves grease, gum, and other substances while displacing water. It’s perfectly safe for all types of metal. This provides a bit of lubrication to prevent future rust or corrosion problems.

You might want to think twice about using this oil for things such as water valves, pond or well pumps just in case contamination might be an issue.

It seems that users have tried Kano Aerokroil on just about everything under the sun, from bathtub faucets and handles to the bolts on a catalytic converter.

Interestingly enough, several people mentioned that Aerokroil didn’t smell as bad as Blaster, which is strange because I never thought Blaster smelled that bad.

Most users stated that Kano Aerokroil does exactly what it says it would do and they were happy campers. Several mentioned that it smelled good and most say that this is their favorite penetrating oil.

I did find users who didn’t think this worked any better than other, less expensive penetrating oils. But there are always people who find products not to their liking. In this instance, they were really in the minority.

If you need an aerosol penetrating oil, I think you will be really pleased with the results you get from this product.

Deserving of a Mention

The darn good penetrating oil with the funny name.

I want to mention this penetrating oil because I saw so many mentions of it on a variety of automotive threads. When aircraft mechanics mention a product, everyone stands up and takes notice. Including me!

Strange as the name sounds, Mouse Milk is considered by many to be the best penetrating oil on the market, hands down. Several aircraft mechanics have stated in forums that they won’t use anything else since this product works where others fail.

The word most often mentioned when describing Mouse Milk is “superior.” It’s not often that you see that word associated with penetrating oils, quite frankly.

Most users say that nothing has worked as well as Mouse Milk and that this product doesn’t just loosen rust, it dissolves it!

Even users who aren’t completely enthused about this oil say that it worked well. They just had other issues with it, such as the bottle was leaking.

If you are interested in trying something new, you can give Mouse Milk a try. See if you agree with other users that this penetrating oil is superior to others.

Best penetrating oil for spark plugs

It’s a fact that some penetrating oils work better for some applications than others. In this case, you probably won’t find a better oil for spark plugs than Knock’er Loose.

This oil is super safe to use as it is registered as safe to use in meat or poultry plants and it is VOC compliant.

Knock’er Loose is designed to work its way into seams and threads.

This works on a variety of applications and metals, including aluminum and cast iron. Users state that this is super slippery and oily feeling, which might be why it works so well.

You might want to avoid getting this oil on hands or clothing. Several people have mentioned that it stains and that it smells like engine oil.

This also works well on spark plugs in other applications besides cars, such as chain saws, motorcycles, boats, and snowmobiles.

A lot of users said that this worked really well for removing spark plugs and exhaust bolts. If it matters, some say that this smelled exactly like Kroil.

A small number of users didn’t find that Knock’er loosened or worked any better or worse than other penetrating oils.

If you are working on some tough spark plug removal jobs, or If you have frozen spark plugs regularly, I wouldn’t hesitate in recommending this penetrating oil for you.

How do penetrating oils work?

The very name “penetrating oil” tells you that a particular oil is not necessarily so much of a lubricant. A penetrating oil is so thin that it can penetrate between two very tight or narrow spaces.

Penetrating oil leaves a thin film of oil on the surface or within the pores of an object, displacing water, or other fluids.

These types of oils have an exceptionally low viscosity. The surface tension allows it the oil to get deep into the smallest of spaces or cracks and crevices.

Sometimes called penetrating fluid, these oils are very volatile. That means under certain conditions they can ignite.

Never use penetrating oils for anything other than its intended purpose. You should be using just enough lubricant to “remove” two parts that have become frozen together.

Is penetrating oil the same as WD 40?

WD-40 is a water-displacing spray and penetrating oil. This is one of the oldest and best-known names of penetrating oils.

WD-40 is often misused strictly as a lubricant, but it doesn’t work as well for that purpose. While penetrating oils can leave behind a very thin film of oil, WD-40 and other penetrating oils are designed to displace water and other unwanted compounds.

It note only helps to remove rust, but allow two parts to either be removed from one another (such as a frozen bolt in a cylinder head) or to move smoothly again.

The problem with using penetrating oils such as WD-40 as a lubricant (such as for a squeaky door hinge) is that they attract dust and dirt.

While it works initially, it actually makes things worse over time. The accumulation of dirt and dust particles will work themselves into the part and cause future wear and tear, as well as more noise.

What can I use instead of penetrating oil?

There are probably a dozen old fashioned remedies that people have used in the past or used when they were in a pinch and had nothing else.

Some of these include:

  • Canning Wax (the type sold to seal a Mason canning jar lid)
  • Beeswax
  • Automatic Transmission Fluid
  • Vegetable Oil

One old recipe that I watched my father make was to mix two parts automatic transmission oil with one part acetone. No fancy bottles.

My dad would go right for my mother’s nail polish remover and mix that with the transmission fluid in his metal, manual pump squirt bottle. He would shake it really well before using it. He swore by that method.

Can you use penetrating oil on spark plugs?

Doesn’t everyone? Just kidding.

Actually, that was the first place I used a penetrating oil. It was to remove some really rusted spark plugs on my “learner” car, a 1965 Ford Galaxy. I can’t remember which brand I used but I remember applying what was probably too much around the plugs and letting it soak in overnight. Those plugs came out fairly easily the next morning.

Using penetrating oil to remove spark plugs is perfectly fine. Finding oil on the spark plugs once you remove them, well, that’s not so fine but that is another story.


If you could only afford to have one can of penetrating oil, I would go with the B’laster PB oil.

When it comes to breaking down the corrosion that is holding a bolt or nut in place, you can’t beat this low viscosity penetrating oil.

It was hard to choose the best since it seems like some work better in some applications than others. But for the best overall, one size fits most category, it’s got to be Blaster. Even though some people think it smells like a skunk.

I like Blaster because in most cases, you can spray, go get a soda from the fridge, finish that soda, and the job is done.

That nut or bolt will break free. It works really fast most of the time. For super hardcore cases, I’ve soaked the part really well and left it overnight. But that often wasn’t necessary.

I’m always one to want to try new things but Blaster has been around for decades and it works. At the end of the day, that is what you want, right?

Get B’laster and get that part moving!

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