Detecting Fuel Dilution in Engine Oil

Fuel dilution can be caused by a variety of factors, with most relating to mechanical issues.

• The process of combustion involves the burning of fuel. There are chances of it entering the crankcase during this time and coming in contact with the lubricating oil. The piston rings are designed to separate oil and the exhaust. It is important for ensuring balanced cylinder compression. If the rings are dirty or damaged, there is a chance that they will fail to seal properly. This increases the chance of fuel leaking and lubricating oil mixing.
• Defective fuel injection can lead to fuel dilution. A poorly atomized fuel may not burn completely and have a higher chance of entering the oil.
• Malfunction in fuel injection system
• Blocked air filters
• Damaged injectors or wrong spray pattern

Both the oil and engine start to experience effects once the fuel is added to the oil. There is a significant decrease in the viscosity of the lubricating oil. As fuel thins the oil, the oil fails to support the load in the engine and does not form a sufficient film to keep engine parts separated.

In addition, fuel removes oil and additive films from the cylinder walls during cylinder liner washdown. This leads to accelerated wear and premature engine failure.

Fuel dilution in lubricants can be determined directly by Gas Chromatography (GC) employing ASTM methods D3524, D3525, and D7593. This method is used to analyze a sample of oil by injecting a portion of it into it. By vaporizing the sample, the GC passes it through an analytical column and separates it into its component hydrocarbons as per their boiling points, with the lighter ones coming off first and the heavier ones coming off last. These components are then measured and identified using detectors

Flashpoint is the lowest temperature at which an ignition source results in the vapours of the test sample igniting/burning under specified conditions of the test. A flash point test has been used for decades both to evaluate new and used lubricants. It can detect fuel dilution in used oil samples. There will be a decrease of 20°C in the flash point temperature if fuel is present. It is strictly a pass-or-fail test. A heavier fuel, such as biodiesel, will not significantly alter the measured flash point. The ASTM D92 is one of the most popular methods of flash point testing.

FTIR Testing, commonly used to detect contaminants and byproducts, can detect the presence of dilution in the oil sample. Although FTIR spectroscopy offers rapid, the user-friendly measurement for fuel dilution, distinguishing between fuel hydrocarbons and those already present in the base oil is difficult. Achieving accurate results is a big task. For calibration, large datasets of narrow-scope samples are required to develop algorithms correlating the fuel dilution spectrum. Hence, FTIR Spectroscopy is not a preferred testing method in most cases.

Chem-Tech is a global leader in fuel dilution and diesel engine emission testing. With more than 25 years of experience, they have developed advanced laboratories. We conduct a range of tests to suit all needs. Our team offers fuel dilution tests to measure the effect of pollutants on the performance and durability of engine oils. So, keep your engine oils in check; contact Chem-Tech for accurate fuel dilution tests. Get in touch today!