What Causes Oil Contamination?

If you’re like most business owners or maintenance managers, you’re always looking for ways to save money and cut costs. Unfortunately, many people overlook one of the biggest sources of potential savings: oil contamination prevention. By implementing a few simple best practices, you can avoid costly engine repairs and keep your business running smoothly. In this blog post, we’ll discuss the dangers of oil contamination and the most common contaminants you’ll find. Read on to learn more!

Why is Oil Contamination Bad?

While some oil contamination is the result of the oil doing its job, it’s not good for your machinery and it eventually reduces the oil’s effectiveness. As your oil is less effective, it impacts the condition and function of your assets. This can lead to equipment breakdown, costly unplanned downtime, or even a critical machine failure. Also, oil contamination can greatly increase maintenance costs. For example, if you buy premium oil but don’t follow best practices to keep it clean, you will end up purchasing more oil due to increased breakdown and the need for oil changes. Understanding and preventing oil contamination as much as possible just continues to improve your lubrication management plan and asset reliability.

What Causes Oil Contamination?

Lubricant or oil contamination can come from either external factors or internal reactions or breakdown. Additionally, oil contamination can happen before you receive the oil! Tanker trucks, storage containers, dispensing, and even storage conditions can introduce contaminants to the oil. If you don’t take preventive action, such as filtering, then you are most likely introducing these contaminants to your assets.

What Are the Main Types of Oil Contamination?

External Contamination

The first type of oil contamination is from external factors you can more easily control. They include things like dirt, dust, water, and cross-contamination with other lubricants. If you keep your machine or storage containers in an unfavorable environment, your oil is at a greater risk of contamination. For example, a space with high humidity, extreme temperature changes, or a lot of dust in the air will not be good for your oil. Simple actions like changing the oil to sampling have the potential to introduce these environmental contaminants to your machine. Furthermore, if you use funnels or dispensing containers that are not wiped clean before use or are used for multiple different lubricants, you can cause oil contamination. In the case of cross-contamination with other lubricants, the two oils may react negatively and create gunk that clogs your machine and causes equipment breakdown.

Internal Contamination

Next, the second type of oil contamination is from internal factors. This kind of oil contamination may be metal particles from surface degradation, contaminants from engine operation, or the result of oxidation or depletion of additives over time. For example, the oil in a diesel engine will be contaminated with soot from engine operation. Another example is water contamination from water-cooled equipment. Typically, you cannot prevent or avoid internal oil contamination, as it’s a result of operating your machine. However, you can monitor contaminant levels to make sure you change the oil before the contaminants build up enough to impact your machinery.

The Most Common Oil Contaminants


Out of all the possible oil contaminants, abrasives have the biggest impact on your assets. Abrasive oil contaminants include dust, dirt, and metal particles from engine wear. Dust and dirt can find their way into your oil at many points in the transport, storage, and dispensing process. However, they can also come from unfiltered air entering the engine. The metal particles in oil come from two sources. First, normal engine usage creates wear on metal components. Second, the buildup of abrasive oil contaminants can cause additional wear beyond the normal level and introduce even more particles to your oil.


On average, water is the second most common cause of oil contamination. It may be a byproduct of engine combustion at lower temperatures or from humidity during storage. Water in your oil can increase wear and cause corrosion of components. Also, it encourages the production of acidic gases that further increase corrosion.


Another term for fuel contamination is fuel dilution. This means that fuel finds its way into your oil, diluting it. This decreases the oil film strength and actually leads to higher oil consumption, which impacts your maintenance budget. Furthermore, fuel dilution lowers the protective properties of oil and its additives by decreasing oil viscosity. That means your oil won’t provide as much protection from corrosion, further increasing component wear.


If you have coolant in your oil, that’s a sign of other engine problems to address. A blown head gasket can often result in coolant contaminating your oil. Similar to fuel dilution, this causes oil viscosity to drop. In fact, the oil may thicken to the point of turning into sludge that can damage engine components.

Next Steps

While some lubricants claim they are superior at resisting the effects of oil contamination, that isn’t the only solution. There are best practices for storage, dispensing, filtering, and monitoring oil to prevent external contamination and track internal contamination. Furthermore, routine oil analysis is an essential part of your lubrication management program. It determines your contaminants, which allows you to revise your plan. Whether you opt for an in-line oil analysis sensor or send samples to a lab, you need data on your oil contamination. Once you have visibility into the state of your oil, you can make improvements to avoid equipment breakdown, expensive repairs, and unnecessary oil changes.

There are so many components to a world-class lubrication management plan. While Redlist isn’t going to solve all of your oil problems, we can help with organizing your data and automating your plan. Contact us if you’d like a partner in improving your lubrication and asset reliability.

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How Oil Film Impacts Bearing Lubrication

Bearings are critical to the reliability of machines. A machine’s ability to perform depends on the health of its bearings. And maintaining bearing health depends on proper lubrication. In our previous webinar with Reliability Solutions’ Tim Dunton, we talked about the steps in achieving and maintaining a successful lubrication program. In doing so, we also talked a lot about lubricating bearings.

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