Oiled Vs. Dry Air Filters

Oiled Air Filters

Enter the oiled air filter, a staple among high-performance manufacturers. Oiled air filters are commonly available as drop-in style replacements, universal conical filters, or cold air intake kits. 

These filters are constructed from high-flow synthetic or multi-layer cotton filter media surrounded by durable stainless steel wire mesh for rigidity. Silicone seals, couplers, and end caps finish the filter’s construction, forming an air-tight seal to prevent unfiltered air from entering the intake.

Oiled filters are—you guessed it—oiled. A specially-engineered oil is applied to the filter media, wetting but not overly saturating the air filter. This oil layer acts as a glue, capturing fine particulate matter that may otherwise slip through the air filter’s pores.  

While typically more expensive than comparable dry air filters, oiled filters feature several benefits that make up for the price difference. Unlike dry paper-based air filters, which require replacement at manufacturer-recommended service intervals, oiled air filters are washable and reusable. When it comes time to service your vehicle's engine air filter, remove it, thoroughly clean it, re-apply filter oil, and reinstall it to enjoy the benefits of a brand-new air filter!

Dry Air Filters

Second on the list is a dry engine air filter, installed as factory equipment on most makes and models. Dry filters are frequently found as factory-style replacements; however, several performance manufacturers offer a limited line of conical dry filters. 

In factory-style applications, dry air filters are typically constructed using polyester or layered paper media with integrated polyurethane seals. However, most dry conical filters feature a dry, synthetic filter media for maximum airflow. 

Unlike oiled filters, dry engine air filters don’t utilize any auxiliary oil on the media. Instead, they rely on heavily-layered, low-micron filter media for excellent filtration. While dry air filters may provide more efficient filtration, they’re also slightly more restrictive than comparable oiled filters. 

Though dry air filters do require replacements at each manufacturer-recommended service interval, they also come with benefits over the oiled-cotton variety. Regarding price, dry air filters are typically less expensive than oiled-cotton air filters, saving you the initial upfront cost. 

Additionally, dry air filters are typically easier on sensitive engine electronics, like MAF (mass air flow) sensors, MAP (manifold absolute pressure sensors), and IAT (intake air temperature) sensors.

Choosing the Right Air Filter

So which style of air filter is right for you?  

Regarding filtration, both dry and oiled air filters offer excellent protection against dirt, dust, and other contaminants. However, dry filters tend to have a slight advantage in overly dusty, sandy, or silty conditions. 

Due to their low-micron media, dry air filters filter approximately 99 percent of contaminants, vs. oiled air filter’s 98 percent; while a small advantage, an advantage nonetheless. Additionally, oil filters often clog up quicker in filthy and dusty environments due to their use of tacky filter oil–another point for dry filters. 

Regarding airflow, oiled air filters tend to take the victory. With less-porous media designed exclusively for performance, oiled air filters typically net slight gains over traditional dry filters. In high-output, heavily-modified applications, you’ll likely be better off with an oiled engine air filter. 

Regarding cost-effectiveness, dry air filters have a lower initial cost; however, they typically require replacements at 12,000 to 15,000-mile intervals, compared to the indefinite lifespan of washable and reusable oiled air filters. In the long run, reusable air filters can save you some money; however, remember that most reusable air filters require you to purchase additional filter recharge/cleaning kits.   

Ultimately, both styles of air filters are extremely functional and offer excellent filtration and performance. Unless you’re operating the vehicle in an extremely dirty environment or attempting to squeeze as much power as physically possible from the powertrain, either type will be more than satisfactory. 

When it’s time to replace your ride’s air filter, check out RealTruck’s extensive inventory. We offer a wide variety of replacement air filters for nearly all makes and models, including OE-style filters, universal conical air filters, and replacement filters for your aftermarket cold air intake system. 

Be sure to utilize RealTruck’s vehicle selection tool to filter results to fit your particular year, make, model, and engine size. Also, be mindful of “universal” conical air filters; most modern vehicles require vehicle-specific filters for proper fitment and adherence to federal/state emissions.