Inhibited VS Uninhibited Transformer Oil- Which is Better to Pick

Choosing the right transformer oil can be difficult as there are so many options available on the market. How do you know which is the best for your needs?

There are two of the most common types of transformer oil: inhibited and uninhibited. Both of these oils have their advantages and features that make them apart from each other. Though both these oils are great, which one is better inhibited VS Uninhibited transformer oil?

Though there is not much difference between them, the things that make them slightly ahead of each other are their viscosity and temperature. But at the end of the day, it depends on people’s personal preferences regarding which one is suitable for whom.

In this article, we will try to compare these two transformer oils. By the end of this article, you’ll be able to pick the right transformer oil for your needs. So, let’s get started with it.

Inhibited VS Uninhibited Transformer Oil

A Comparison Table between Inhibited VS Uninhibited Transformer Oil

If you’re in a hurry, then we would suggest you check this table. This comparison table will help you know about the differences between these two oils.

FactsInhibited Transformer OilUninhibited Transformer Oil
Oxidation ResistanceMore ResistantSlightly Lower
PerformanceSuperiorSame as Inhibited
Shelf LifeLast for up to Two YearsLast for Just a Few Months
TemperatureGood for Warm TemperatureGood for Cold Temperature
MaintenanceNeed Less MaintenanceNeed High Maintenance

Inhibited VS Uninhibited Transformer Oil- Head-to-Head Comparison

Transformer oil is an essential fluid used to cool and protect electrical equipment. It plays an important role in the performance and efficiency of the equipment. It is available in two main forms, inhibited and uninhibited, and each type has its unique properties and advantages.

Check out the key differences between Inhibited VS Uninhibited transformer oil and pick one that is suitable for you.

Oxidation Resistance

Inhibited transformer oil is more resistant to oxidation as compared to uninhibited transformer oil. In the event of a fire, the smoke produced will be less harmful with inhibited transformer oil.

The other benefits of using an inhibited transformer oil are that it has a longer shelf life and can be used in a wider temperature range.

So, inhibited transformer oil is the better option for electric transformers, as it provides superior protection against oxidation. However, uninhibited oil can be used in certain situations where oxidation resistance is not as important.

Ultimately, each transformer system is unique, and the best oil for the application should be chosen based on specific requirements.


When it comes to the performance of inhibited and uninhibited transformer oils, it’s a bit more complicated than just stating that one is better than the other. Usually, uninhibited transformer oils are better in terms of various facts. However, there are some cases where inhibited transformer oils outperform their uninhibited counterparts.

The choice between inhibited and uninhibited transformer oils ultimately comes down to your specific needs and what you’re looking for in oil. If you’re looking for an oil that will have a long shelf life and perform well in a wide range of temperatures, uninhibited transformer oils are the way to go.

However, if you’re more concerned with the maintenance and ensuring that your oil doesn’t oxidize as quickly, then inhibited transformer oils may be a better option for you.

Shelf Life

The shelf life of inhibited transformer oil is significantly greater than uninhibited transformer oil. Uninhibited transformer oil will only last for a few months without undergoing any type of oxidation, while inhibited transformer oil will last for up to two years without any negative effects. This is due to the inhibitors that are present in the inhibited transformer oil, which work to protect the oil from any oxidative damage.

Temperature Range

The temperature has an important role in the performance of transformer oil and the life of your machine. Modern transformers use a wide range of oil types to increase their efficiency, but which type works best in hot and cold climates?

Inhibited transformer oils are best suited for high-temperature applications and will usually provide good cooling properties up to 110°C. Uninhibited oils tend to have a lower thermal load but have much lower oxidation resistance than inhibited oils. In warmer climates, this is ideal, as the oil can maintain its performance for longer periods.

In colder temperatures, uninhibited transformer oil performs better as it has a narrower viscosity index and is less likely to thicken and become viscous at low temperatures. It’s also more resistant to thermal degradation, allowing it to handle higher current loads without getting damaged.


In terms of maintenance, inhibited transformer oil requires less maintenance than uninhibited transformer oil. This is because the additives in the inhibited transformer oil help to keep the transformer components protected and reduce the chances of sludge and varnish deposits forming.

On the other hand, uninhibited transformer oil requires more frequent maintenance as it does not contain any additives and is more prone to the formation of sludge and varnish deposits.


Cost is always an important factor when considering different types of DBPC transformer oils. Uninhibited transformer oil is usually cheaper than inhibited transformer oil, however, the price difference between the two can depend on the quantity you’re buying and the specific supplier.

For example, a gallon of uninhibited transformer oil may cost around $20 – $25 compared to $30 – $35 per gallon for inhibited transformer oil, so the price difference might not be that significant if you are only buying a small amount. However, if you’re purchasing larger amounts, then the cost difference could add up quickly.

Not just the initial purchase cost, you also need to consider ongoing costs such as maintenance and replacement. Inhibi­ted transformer oils are more expensive upfront but may save money in the long run because they require less maintenance and last longer than uninhibited transformer oils. This needs to be taken into consideration when making a decision about which type of oil is best for your project.

Inhibited VS Uninhibited Transformer Oil

Inhibited and Uninhibited Transformer Oil- The Winner

So which type of APAR transformer oil is better—inhibited or uninhibited? To answer that question, it’s best to weigh the pros and cons of each. Both inhibited and uninhibited oils can provide long-term oxidative stability and offer reliable performance in temperature ranges of -94 to 302 degrees Fahrenheit. However, inhibited transformer oil may be the better option when it comes down to it.

Inhibited oils are more oxidation-resistant than their uninhibited counterparts and help preserve electrical properties for longer than an uninhibited solution can. It also has a lower cost of maintenance which can save you money over time. And lastly, when compared against uninhibited oils, inhibited transformer oils tend to last longer due to their formulation that’s designed for extended periods of service.

So, when you’re trying to decide between inhibited or uninhibited transformer oil, inhibited might be the winner—as it usually provides a greater return on investment in terms of performance and costs over time.

Frequently Asked Questions

Q. What is an inhibitor in transformer oil?

Inhibitor in transformer oil is an additive used to protect the transformer from oxidation, corrosion, and other forms of degradation. It helps to prolong the life of the transformer by preventing the formation of sludge, acid, and other contaminants in the oil.

Q. What is the neutralization value of transformer oil?

The neutralization value is the determination of the acidic content of transformer oil. The neutralization value is measured in milligrams of KOH required to neutralize the acid present in one gram of oil. As the oil becomes acidic, the water content of the oil becomes more soluble in the oil.

Q. What is an oil-immersed transformer?

Oil-immersed transformers use oil for insulation purposes, stopping discharge and aura discharge and at the same time dissipating the heat of the transformer.

Q. Why is transformer oil called mineral insulating oil?

Transformer oil is also known as transformer mineral oil which is a highly refined mineral oil derived from petroleum. It is a type of dielectric fluid used in transformers and other electrical equipment for insulation and cooling purposes. The oil is processed to remove impurities and improve its electrical insulating properties and stability.

Final Thought

After the comparison, it can be undoubtedly said that inhibited transformer oil is the clear winner. But it doesn’t mean that uninhibited oil is not good enough. Ultimately the decision is up to you to pick between inhibited vs uninhibited transformer oil. Thanks for reading this article.

READ ALSO: Parafin Vs Napthanic Transformer Oil


I am Engr. Z Eusuf Lubricant Specialist, Mechanical Engineer & has been working with engine lubricants for a long time and knows what makes them work best. I can help you find the right oil for your needs, and I have tips on how to keep your engine running at its best.