Change Oil In A 2005 Fat Boy

A Fat Boy’s oil drain plug is centered between the motorcycle’s hidden shock absorbers.

Changing the engine oil on your Harley-Davidson Fat Boy for the first time can be puzzling since contemporary Harley-Davidson motorcycles use three separate fluids. With the engine oil housed in a tank under the rider’s seat, one must first find the oil drain plug, which is hidden between the Softail’s shock absorbers under the frame, before the oil can be changed. Once the drain plug is located, a few simple tools and fresh oil are all you need to finish the job.


1. Place an oil pan directly under the engine oil’s drain plug. Use a socket wrench to remove the drain plug. Allow the oil to drain completely.

2. Pull the O-ring off the drain plug and replace it with a new O-ring. Clean the tip of the drain plug with a shop towel to remove any debris that may be stuck to it. Reinsert the drain plug into the motor and tighten with a socket wrench.

3. Move the oil pan to the front of the motor and place it directly beneath the oil filter. Unscrew the oil filter with an oil filter wrench and allow any remaining oil to drain from the motor. Discard the old filter.

4. Fill the new oil filter with oil and spread a thin layer of oil around the filter’s mating surface with your finger. Screw the new filter onto the motor by hand until it is seated. Wipe away any spilled oil with a shop towel.

5. Remove the oil tank’s filler cap and slowly add oil into the tank. Do not add more than three quarts of oil. Wipe away any spilled oil and replace the filler cap.