The fuel quality hydrometer provides a general indication of fuel quality and should not be considered to be scientifically accurate.

1. Drain the fuel filter housing by following the steps below:

•	Stop the engine.

•	Place a container under the water drain valve exit hose at the left front side of the engine.

•	Open the drain valve.

•	Use a scan tool in order to command the fuel lift pump ON.

•	Fill a 1 liter (0.946 quart) container with a sample of fuel.

•	Close the drain valve.

2. Obtain a fuel quality hydrometer (J 38641-B ).
3. Fill the hydrometer with the fuel sample by doing the following:

•	Squeeze the hydrometer bulb.

•	Submerse the hydrometer tip into the sample.

•	Release the bulb, allowing fuel to enter the glass tube until it completely floats the glass bulb inside the tube.

•	Gently spin the hydrometer in order to relieve the surface tension of the fuel sample.

4. Read the scale on the glass bulb at the point where the top of the fuel sample contacts it.

•	Reading this value will indicate an approximate fuel oil specific gravity. Refer to tool instructions on how to determine API Gravity.

•	Refer to Fuel Oil Specific Gravity Requirements table.

5. If the correct fuel is being used in the conditions listed in Fuel Quality and meets the number 1-Diesel or the number 2-Diesel fuel oil specific gravity requirements, the fuel is OK. If not, the fuel should be replaced.