Oil degradation & fuel dilution
Oil degradation and fuel dilution are two critical issues that can affect the performance and longevity of a vehicle’s engine. Both are interrelated and can cause significant damage if left unchecked.
What is fuel dilution?
Fuel dilution occurs when engine oil and fuel get mixed, resulting in a significant decrease in the oil’s viscosity and lubricating properties. This can lead to premature wear of engine components as well as reducing the engine life. Fuel dilution may occur in modern direct injection engines when they idle for extended periods of time or have broken or faulty injectors.

One of the most common causes of fuel dilution is incomplete combustion. When the fuel does not burn completely, it can enter the engine oil and subsequently reduce its properties. Dilution can also be caused by engine idling, aggressive driving, and short trips. These actions can cause the engine to run cooler than usual, which keeps the engine from completing the combustion process, increasing the risk of fuel dilution.  

What about oil degradation?

Engine oils are designed to lubricate their components, reduce friction, wear, contaminants and heat. However, the oil breaks down over time, and its properties lose effect. The reduction or loss of oil effectiveness is called degradation, and it can lead to reduced fuel efficiency and increased engine wear. 

Some of the most common factors that can cause oil degradation are contamination, high temperatures, and oxidation. Contamination, such as dirt, debris, and moisture, can reduce the oil’s lubrication abilities. High engine temperatures break down the oil quicker, leading to ineffectiveness, and oxidation occurs when the oil reacts with oxygen and degrades. 

What are the consequences of these two issues…?

Both oil degradation and fuel dilution can have severe consequences for an engine. If left unchecked, they can generate significant damage to the machine, increasing repair costs and substantially decreasing the engine´s lifespan. Fuel dilution not only impacts the oil’s viscosity and engine performance but can also reduce fuel efficiency and increase engine wear and oil consumption while also causing varnish and sludge. 

Oil degradation, on the other hand, reduces the effectiveness of the lubricating properties and the engine cooling, leading to increased friction and heat. As with fuel dilution, degraded oil can also cause the formation of piston deposits, sludge and varnish in the engine 

If not timely addressed, both dilution and degradation can cause irreversible and complete engine failure. 

…and how can they best be prevented?

The most important way to prevent these issues is always following the vehicle manufacturer’s recommendations for oil changes and only using the oils meeting the recommended oil specifications. Doing regular oil changes within the proper timeframes will help remove contaminants and prevent the oil from breaking down. Using the recommended high-quality engine oils is extremely important, as these products need to account for the demands and pressure different engines are subjected to, especially the heavy-duty kind such as the ones found in the agriculture and construction industries.  

VISCOSITY’s UNITEK line of diesel engine oils has been specifically designed for high-demand vehicles, providing extended protection and enhanced performance. With full synthetic, semisynthetic, and regular alternatives, UNITEK is a low-emission diesel oil that protects your engine against soot buildup and deposits, keeping it clean and performing at its peak even under severe mechanical stress and low temperatures. This is just one of the many products VISCOSITY Oil has formulated to protect heavy-duty equipment, a mission that has kept the company on the move for over 130 years and counting. Premium, high-quality products make a difference in maintaining your engine, and VISCOSITY Oil understands the importance of having a trusted solution that can account for the many demands on the field. Counting on reliable, high-performing oil is, therefore, a key aspect when it comes to preventing degradation and dilution, as well as other common engine issues. And word to the wise: once you’ve found a reliable oil, don’t go mixing it with other brands! Even though they might meet the same requirements, the interaction between the two different compositions and the engine could also cause damage.  

Finally, it’s important to address any possible mechanical failure as soon as it is noted. Neglecting to address minor issues such as leaky fuel injectors or worn piston rings—, can result in bigger and more complex malfunctions that can lead to downtimes and additional expenses. Warming up the engine before driving is a good and straightforward preventive measure for fuel dilution – especially on cold days and during the winter season – as the engine reaches its optimal operating temperature quicker. It is also essential to clean the tank regularly to make sure there are not too many particles that might end up reacting with the fuel or clogging the filters and injectors. 

What signs should be paid attention to?

Oil degradation and fuel dilution can be diagnosed with oil analysis tests that measure the engine oil’s viscosity, contamination levels, and chemical composition.  

Some signs that an engine might be facing fuel dilution or oil degradation are: 

  • Reduced fuel efficiency  
  • Increased engine noise  
  • Burning smell from the engine 
  • Hard start or rough idle 
  • Sudden drop in oil pressure or power 
  • If you suspect that there might be something going on with your vehicle, don’t hesitate to take immediate precautions. Remember: high-quality products will make a huge difference, so if your current products are not meeting expectations, you can always switch to a tested solution specifically designed for high demand vehicles and take on the VISCOSITY Oil route of optimal performance, meeting and even exceeding API standards. Acting on time could save both your engine and your wallet! So make a swift and smooth transition into the VISCOSITY Oil Family and check out our product cross-reference guide to continue working in fluid motion with the highest protection for your equipment.  


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