ALTERNATOR-YM 5692855 - Caterpillar

Measuring Fuel Dilution
Diesel fuel is chemically similar to the lubricants that are used in diesel engines. A slow fuel leak will blend the fuel into the oil. Normal operating temperatures may cause volatile parts of the fuel to vaporize. The fuel that remains in the oil is less volatile.A closed cup flash test can be performed in order to detect fuel dilution. The flash test is designed to measure the volatile parts of the fuel that are remaining in the oil. Detecting less volatile fuel is difficult. The lack of volatility reduces the accuracy of the flash test.Since the flash test does not accurately detect fuel dilution, do not use the flash test as the only measure of fuel dilution. Instead, verify the dilution by the following methods:
Gas chromatograph fuel dilution test
Oil viscosityThe test that uses a gas chromatograph is designed to measure fuel dilution in crankcase oils. The gas chromatograph can identify the small chemical differences between diesel fuel and lubricating oil. Even though the gas chromatograph provides a more accurate measure of fuel dilution, always verify the results with the viscosity test.A significant level of fuel dilution reduces oil viscosity. If an unacceptable level of fuel dilution is suspected, the kinematic viscosity of the oil must be measured.Fuel dilution that is greater than 4 percent will usually cause viscosity that is less than the specified viscosity grade. If the oil is still within the specified viscosity grade, fuel dilution is unlikely to have reached an unacceptable level. Use the following chart to determine if viscosity has reached the minimum acceptable level. The guidelines of viscosity in the chart are slightly less than the limits of the SAE viscosity grades. However, these guidelines still provide adequate engine protection.
Table 1
Viscosity Grade Minimum Oil Viscosity at 100 °C with Fuel Dilution Greater Than 4% as Measured by a Gas Chromatograph Action
0W-40
5W-40
10W-40
15W-40 12.0 cSt Investigate the cause of fuel dilution or reduce the engine oil change interval.
0W-30
5W-30
10W-30 9.0 cSt Verifying Fuel Dilution
Always verify fuel dilution by the combination of a viscosity test and a gas chromatograph test. If the result is in excess of 4 percent, investigate the cause.
Obtain an oil test kit. Refer to Table 2.
Table 2
Oil Test Kits
Region Part Number
North America and South America 29990014
Rest of the world 29990011
Follow the instructions that are supplied with the oil test kit.
Obtain a sample of the oil from the engine. Refer to Operation and Maintenance Manual, "Fluid Recommendations - Engine Oil".
Complete the form that is included with the oil test kit.
Send the oil sample for analysis. Follow the instructions that are included with the oil test kit.