Understanding the impact of liquid fuel on engine durability
By Lake Speed Jr.
Engines, whether powered by gasoline or diesel, rely on the combination of fuel and air to produce combustion. While it might sound like clickbait, the reality is that the liquid fuel we pour into our engine can indeed become its enemy, adversely affecting engine durability. In this article, we will delve into the intricacies of how unvaporized fuel can lead to issues such as fuel dilution and soot contamination, which impact the overall health of your engine.
Liquid Fuel is the Real Problem
In the combustion process, neither gasoline nor diesel engines burn the liquid fuel outright; rather, what combusts is the vaporized fuel. Unfortunately, not all the fuel vaporizes, leaving behind unburnt fuel that becomes a contaminant. This unvaporized fuel can lead to various problems, including diluting the oil and washing it off the cylinder walls. Additionally, carbonized fuel that does not combust transforms into soot, further complicating engine health. Oil is the lifeblood of the engine, and fuel dilution and soot contamination are like bad cholesterol in your blood – high levels mean bad things are likely to happen.
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Fuel Dilution
Fuel dilution occurs when liquid fuel finds its way into the engine oil, lowering the oil’s viscosity. Reduced viscosity is detrimental, as it increases wear and can result in lower oil pressure, potentially causing bearing wear. Used oil samples often reveal a correlation between high wear and increased fuel dilution. In looking at used oil samples every day, 9 times out 10 there is high fuel dilution when there is a high level of wear. You can see it in bearing materials like Copper, Tin and Lead. You can also see it in cylinder bore and piston ring materials like Iron and Chromium. If the fuel dilution exceeds 3%, the Parts Per Million(ppm) of these wear metals increases. Notably, direct injection (DI) engines tend to exhibit higher levels of fuel dilution compared to port injection systems. This is due to the shorter amount of time for the fuel to vaporize.
Soot
Ever wondered why diesel oils turn black? The answer lies in soot, hard carbon particles formed from unburnt diesel fuel. Because Diesel engines provide the shortest amount of time for the atomized fuel to vaporize, diesels create the most soot. It doesn’t help that diesel fuel tends to not vaporize as easily as gasoline. Just look at the concrete near the gas pumps at any gas station that also sells diesel. When the high combustion pressures and temperatures carbonize the fuel, it becomes soot, and that soot acts as an abrasive, causing wear in the engine. Cylinder bore polishing and rocker arm wear are consequences of soot contamination in the oil. These are common issues in diesel engines, and the Diesel OEM’s actually use Carbon Black as a soot surrogate to “pre-soot” diesels oils when they run engine durability tests. Soot handling is one of the major chemical differences between Gasoline engine oils and Diesel engine oils.
How to Identify Fuel Dilution Problems
Simply put, used oil analysis provides valuable data for diagnosing fuel-related issues. This analysis provides crucial information, including the exact percentage of fuel dilution, the extent of viscosity loss, and the percentage of soot contamination. Monitoring these parameters allows for a proactive approach to engine maintenance.
Mitigating Fuel-Related Issues
Knowing there’s a fuel dilution problem is only the first step; addressing it is crucial for engine longevity. Effective fuel additives, such as polyetheramine (PEA) for gasoline engines, can mitigate fuel-related issues. Ensuring clean injectors is equally important, as they atomize fuel more efficiently, promoting better vaporization. This holds true for both gasoline and diesel engines. In the US, Diesel fuel is not required to have detergent additives, so utilizing a Diesel fuel detergent additive can make a huge difference. Additionally, using the appropriate fuel type for the season, such as avoiding summer blend gas in winter, and selecting oils specifically designed to handle diesel soot contribute to overall engine health.
Conclusion
Understanding the nuanced ways in which liquid fuel can impact engine performance is essential for maintaining a healthy and efficient engine. From fuel dilution to soot contamination, these issues can be identified through diligent oil analysis. Armed with this knowledge, vehicle owners can take proactive steps to mitigate fuel-related problems, ensuring their engines run smoothly for the long haul.
To view this article with all images in the digital version of Engine Professional magazine, go to https://engineprofessional.com/2024EPQ1/#p=22