The diesel fuel hydrometer is used for troubleshooting engine performance problems and measuring diesel fuel quality. Mack suggests using the following procedure when using a hydrometer:
Figure 1* Draw sufficient fuel into the hydrometer to completely float the bulb inside the glass tube (see Figure 1).
* Close the siphon tube using a tube clamp.
* Take an American Petroleum Institute (API) gravity reading from the top scale indicated by the fuel line on the floating bulb (see example of an API gravity reading of 45 as shown in Figure 2).
* Take a reading from the bottom temperature scale indicated by the mercury level on the floating bulb (see Item 1 in Figure 3 for an example of a temperature reading of 76ÂşF). Temperature is measured in Fahrenheit and used to determine the variable factor shown on the right side of the temperature scale (see item 2 in Figure 3 for an example of a variable reading).
* Add or subtract the variable factor (based on temperature) to the API gravity measurement. The result is the correct API gravity for diesel fuel.
Figure 2See Figure 4 for Mack’s recommended API gravity ranges for Type 1-D and Type 2-D heavy vehicle diesel fuel.
Figure 3
Figure 4
