Oil Aeration 101: Causes, Effects, and Solutions for Engine Protection

Oil aeration can cause serious issues in high-revving race engines, leading to pressure loss, cavitation in the oil pump, and even long-term engine damage. But what exactly is aeration, and how can it be minimized? Understanding how air enters the oil system, the various types of aeration, and the potential damage it can cause is essential for protecting your engine. In this blog, we’ll break down the basics of oil aeration, its effects on engine performance, and offer some practical tips on how to prevent or reduce aeration to protect your engine from its harmful consequences.

WHAT IS OIL AERATION?

Aeration, otherwise known as air contamination, happens when air makes its way into your engine oil. It can show up in four different ways; entrained air, foam, dissolved air and air pockets.

ENTRAINMENT

The most common form is called entrainment, where tiny air bubbles become trapped in the oil as it circulates through the lubrication system. There are lots of chances for entrainment to occur, especially in race applications; faster engine speeds create more bubbles, leading to more air in the system. Other factors, like churning from the crankshaft, suction through the oil pump, and reduced resting time in the oil pan, can all contribute to air binding to the oil.

FOAM

Entrained air will eventually rise to the surface of the oil and try to escape. Depending on the oil’s viscosity and the engine’s temperature, the vibrations and movement from a running engine can whip those surface bubbles into foam. As the foam forms a layer on top of the oil, it can spread throughout the lubrication system, hindering the oil's ability to lubricate and cool vital engine components.

DISSOLVED AIR

Another form of air contamination is called dissolved air. When air in the system becomes pressurized, it transforms into dissolved air. This form of aeration is particularly deceptive, as it mixes with the oil at a molecular level, so it’s basically invisible. The oil will not appear to be aerated, and there won’t be any visible bubbles, but it can still cause significant damage over time.

AIR POCKETS / FREE AIR

Air pockets, otherwise known as free air present another common risk of air contamination, often forming during maintenance services when the lubrication system is unsealed. These pockets can become trapped during oil changes, system flushes, or when seals and lines are replaced. If not quickly addressed and purged, these air pockets can prevent proper oil flow to internal components, leading to potential oil starvation.

HOW DOES AIR CONTAMINATION AFFECT YOUR ENGINE?

Aeration, whether through entrainment, foam, dissolved air, or air pockets, can cause severe engine damage. Oxygen exposure accelerates oil oxidation, resulting in viscosity changes and the creation of harmful sludge, sediment, and varnish. These contaminants clog filters and create blockages, restricting oil flow and affecting performance. Aerated oil can also reduce the effectiveness of the oil wedge in the engine bearings, effectively lowering the pressure at the bearings and increasing the likelihood of metal-to-metal contact.

HOW CAN YOU PREVENT AERATION IN YOUR ENGINE?

Preventing oil aeration is entirely possible with the right precautions. Sealing leaks is crucial, but care should be taken not to introduce air pockets during the process. Once air pockets are detected, they can be purged to maintain proper oil flow. A consistent oil pathway into and out of the pump is essential for reducing air mixing with the oil. High performance oil pumps like IAG’s Stage 2 Oil Pump can be a real game-changer when it comes to prevention. With its precision-machined inlet and outlet passages, the Stage 2 ensures smoother transitions, minimizing entrainment and reducing the risk of cavitation.

MORE PREVENTION TIPS

To further prevent aeration, it’s important to control oil splash, as this is another opportunity for air to mix in with the oil, increasing the chance of entrainment. The IAG Performance Windage Tray is designed to address this by directing oil from the upper crankcase to the lower crankcase and oil pan. Its precision-formed louvers guide the oil downward, preventing it from splashing up into the path of the crankshaft and connecting rods, reducing aeration and promoting smoother engine operation.

DETRAINMENT

Another effective solution is the IAG Performance EJ Street and Comp Series Oil Pans, which incorporate an internally integrated stainless steel baffle designed to minimize oil splashing and reduce the risk of cavitation and oil starvation. The Comp Series Oil Pans also feature one-way baffles to further prevent the oil pickup from being uncovered due to slosh. The pans’ larger capacities also allow more time for air to dissipate from the oil, a process known as detrainment, which enables trapped air to safely rise out before it affects engine performance.

While these strategies provide a solid foundation for minimizing oil aeration, remember that addressing air contamination often requires a multipronged approach. This could involve anything from switching lubricants and adjusting viscosity to sealing the lubrication system more effectively. Foam-eliminating additives might seem like a quick fix, but they often fail to address the root cause of aeration and can sometimes make the problem worse. With a bit of patience and the willingness to refine your setup, you’ll be able to keep your engine running at its best. Of course, if you have any questions or need a bit of friendly advice, feel free to give us a call at 1(410)840-3555 or send us an email at sales@iagperformance.com.