Fighting Rust: Using Engine Fogging Oil To Combat Moisture

As you might have read recently in our exclusive newsletter, Lab Notes, our shop has been subjected to extremely high moisture content in the air this summer, thanks to an unusually active monsoon season. As any of you who live in humid areas know, this airborne water content can wreak absolute havoc on any unprotected metal surfaces in your shop, garage, or really anywhere that isn’t completely climate-controlled and air-conditioned. We talked about a couple ways to combat humidity from desiccants to engine fogging oil.

While we paint parts in order to protect them, there are a number of rust-prone components and surfaces in an engine that are uncoated — and by their nature, can’t be coated. Because of that, they are susceptible to humidity and the subsequent development of surface rust. While desiccation might be an option for small, air-tight areas, for what we’re doing, the only effective way to protect them is with a surface coating. Enter AMSOIL’s Engine Fogging Oil.

What Is Engine Fogging Oil

While the name might seem rather straightforward, the “fogging” part elicited visions of something like bug bombs being set off in the oil pan while the engine was tented. Ridiculous imagery aside, Fogging Oil is an aerosolized oil (it comes in a pressurized spray can) that you spray onto the surface you want to protect.

For a running, assembled engine, whether it’s in a car or on a run stand, just spray it directly into the intake airstream until smoke comes out of the exhaust. The only concern here would be on mass airflow sensor-equipped engines. You want to prevent the oil from hitting that sensor.

The product has been largely focused on small-engine applications, power sports, and personal watercraft, but is incredibly useful on any internal combustion engine. We reached out to AMSOIL’s Len Groom to talk about the Engine Fogging Oil and its uses in EngineLabs-specific applications, only to find more uses than we originally intended.

“These engines need protecting too, and in most situations, it’s the same or similar materials that you’re protecting,” Groom explains, when asked about the suitability of the Engine Fogging Oil on a V8 application. “With a race car, it’s not exposed to as much moisture as say a personal watercraft, but with a four-stroke engine, some of those exhaust valves are left open to the atmosphere when you store it. If that happens to be a damp garage, moisture can really be an enemy.” While the principles of application between the advertised markets and ours are similar, there are some notable differences that Groom was sure to mention.

Fogging The Engine

Typically, the surfaces you’re trying to protect are inside of the engine you’re dealing with. Since most people don’t disassemble their engines when storing them for a period of time, the easiest way to get the product into the engine, is to spray it right into the air inlet while the engine is running. “On a small engine, you spray it into the intake path and keep going until you see a decent amount of smoke coming out of the tailpipe and that’s it,” Groom explains. “Obviously this will take more product on a V8 engine than it will on a small engine application, but the theory is the same. Usually, I tell people if they can kill the motor with it, to do it, but that’s going to be a lot tougher on a V8.”

In an automotive application, there are a couple of considerations to be aware of. The first is for any engine equipped with a mass-airflow sensor. “A MAF sensor probably won’t like this,” chuckles Groom. “So you probably don’t want to let it get on the sensor. If you can find a point on the intake tract to introduce it to the engine, that’s the best call.” That could be a post-MAF vacuum port, the EGR port, or really any place you can spray into, without running the risk of getting any of the oil on the MAF sensor.

For this bare block, we just coated every unpainted surface. Since we'll be wiping down all the critical surfaces before assembly, there's no worry about contamination. The same goes for an assembled short block — just wipe off any gasket surfaces before assembly. Luckily, because we've been oiling the block about every other time we've been in the shop this season, the monsoons' humidity hasn't done any real damage to our block.

In a carbureted application, it gets much simpler, since there’s nothing electronic for the oil to potentially foul. “Just spray it into the throttle as fast as you can until you see smoke come out of the exhaust and you’re done. Keep it alive with the throttle until you see a good amount of smoke, and then you’re good,” says Groom. The same goes for any speed-density EFI system, although Groom does warn that EFI systems will be much harder to choke the engine with the spray, since the computer will be doing its best to adapt to the changing conditions.

Non-Running Engines Need Protection Too

Shifting beyond the application Engine Fogging Oil is marketed for, we asked Groom about its effectiveness with engines and components in various states of disassembly in the shop. We are constantly wiping down the decks, bores, and journals of our different projects with oil in order to try and stave off the dreaded haze that all the moisture in the air is sure to bring.

Once the block is fully coated, go ahead and bag it up like usual. As the propellant flashes off, a highly viscous oil is left behind that not only blocks moisture,  but is also fortified with anti-corrosion agents. Pro tip: make sure you have fresh air moving through the shop and you don’t accidentally set your air conditioning to “recirculate” instead of “fresh air.”

“Spray everything down,” says Groom. “The cylinders, the bearing saddles, anything that is exposed metal, spray it down. The thing about the fogging oil is that it goes on in aerosolized form, and there’s chemistry in there that evaporates everything but the oil. That lets that oil be tacky – it’s some tenacious stuff that hangs onto that metal. Plus there’s also some anti-corrosives in the mix as well.”

That goes for more than just bare components as well. Assembled cylinder heads and assembled short-blocks are treated the same way. Since it’s designed to be sprayed directly into a running engine, there are no adverse effects to be concerned with. “The only thing you would need to do is wipe down the gasket surfaces before assembly and then you’re good to go,” Groom says.

Bonus Uses

As we were talking, it occurred to us that AMSOIL’s Engine Fogging Spray might be the ticket to keeping our mill table and lathe ways rust-free. Since that side of the shop isn’t insulated and keeping those items in pristine condition has always been a battle. “Engine Fogging Oil would actually be perfect for that,” agrees Groom. “We have a heavy metal protector, but the problem is that it leaves a waxy substance behind. In the application of your machines, fogging oil works better, because you don’t want that waxy shell buildup. You just want an ultra-light coating with those precision machined parts.”

Bonus: As you can see, we’ve struggled with the brown haze on our lathe and mill on the uninsulated side of the shop. Luckily, in addition to protecting engines, the Engine Fogging Oil should really help keep our mill table, milling vise, and lathe ways as protected as possible, while not requiring a deep clean to remove the protectant before each use.

Groom did warn that the in that type of application, being open and in a non-cleanroom shop environment, the Fogging Oil might allow dust to accumulate. “The only potential drawback is that it might attract some dust if you’re in a particularly dusty environment. So, in that case, you would just give [the mill table or lathe ways] a wipe down before using it,” concludes Groom.

Now, thanks to AMSOIL’s Engine Fogging Oil, not only can we rest a little easier knowing that our projects are well-protected against excessive moisture in the air. It would be a shame after all that time and effort to have everything properly machined, to have to revisit the machine shop to fix the wrath of water and time.

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Greg Acosta

Greg has spent nineteen years and counting in automotive publishing, with most of his work having a very technical focus. Always interested in how things work, he enjoys sharing his passion for automotive technology with the reader.
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