Step-by-Step Guide to Changing the Fuel Filter on a 2018 Ram 2500

If you own a 2018 Ram 2500 with the 6.7L Cummins diesel engine, you already know how powerful and dependable it is. But like any diesel truck, proper maintenance is key to keeping it running smoothly. One of the most important yet often-overlooked tasks is replacing the fuel filter.

This guide explains how to change the fuel filter 2018 Ram 2500, why it matters, and how it protects your engine and fuel system — with a focus on conditions most U.S. truck owners face daily.

Why Is the Fuel Filter So Important?

A fuel filter removes dirt, water, and debris from diesel before it reaches the injectors. Clean fuel ensures complete combustion, better performance, and fewer emissions.

In the 6.7 Cummins engine, high-pressure injectors are extremely precise. Even tiny particles or traces of water can cause wear, leading to expensive repairs. Replacing the fuel filter 2018 Ram 2500 at recommended intervals keeps your engine protected and efficient.

How Often Should You Change the Fuel Filter on a 2018 Ram 2500?

For most U.S. drivers, Ram recommends replacing the fuel filter every 15,000 miles or once per year — whichever comes first.

However, if you drive in dusty, humid, or rural environments (like Texas, Arizona, or the Midwest), it’s smart to shorten that interval to 10,000–12,000 miles. Diesel fuel in different regions can contain varying levels of moisture and contaminants, which makes regular maintenance even more critical.

What You’ll Need Before Starting

Changing the fuel filter 2018 Ram 2500 is a straightforward DIY job that takes about 30–45 minutes. Here’s what you’ll need:

• Replacement Mopar or Fleetguard fuel filter kit (Part numbers: Mopar 68157291AA and 68065608AA)
  
  

• Oil filter wrench or socket set
  
  

• Drain pan
  
  

• Clean rags and gloves
  
  

• Diesel-rated funnel
  
  

• Safety glasses
  
  

• A few gallons of fresh diesel (optional for priming)
  
  

Using a genuine Mopar or Cummins filter ensures the correct fit, proper micron rating, and reliable water separation — all vital for your truck’s long-term health.

Step-by-Step: How to Change the Fuel Filter on a 2018 Ram 2500

Step 1: Park Safely and Relieve Fuel Pressure

Park the truck on level ground and turn off the engine. Remove the fuel cap to release pressure in the tank. Disconnect the negative battery terminal to prevent any accidental starts.

Step 2: Locate the Fuel Filters

Your 2018 Ram 2500 has two fuel filters:

1. Primary filter – located under the driver’s side near the fuel tank.
   
   

2. Secondary filter – located under the hood, near the engine bay on the passenger side.
   
   

Both must be replaced together for proper system function.

Step 3: Drain the Old Fuel Filter

Place a drain pan under the rear filter. Open the water drain valve and let fuel flow out. Once drained, use a filter wrench to remove the filter canister. Dispose of the old fuel properly according to U.S. environmental regulations (most auto stores like AutoZone or NAPA accept used diesel fuel and filters for recycling).

Step 4: Replace the Rear Fuel Filter

Lubricate the gasket of the new filter with clean diesel. Thread it onto the housing by hand until snug, then tighten an additional ¾ turn with a wrench. Close the drain valve.

Step 5: Replace the Front (Engine Bay) Fuel Filter

Remove the cap using a socket wrench. Take out the old filter element and install the new one. Reinstall the cap tightly — don’t overtighten.

Step 6: Prime the Fuel System

Turn the ignition key to the “ON” position (without starting the engine) for 30 seconds. This activates the lift pump, filling the filters with diesel. Repeat this cycle 3–4 times to ensure all air is removed.

Step 7: Start the Engine and Check for Leaks

Start your Ram 2500 and let it idle for 1–2 minutes. Check both filters for leaks. If there’s no sputtering or rough idle, your installation was successful.

What Happens If You Don’t Replace the Fuel Filter?

Neglecting the fuel filter can lead to:

• Poor throttle response and reduced power
  
  

• Hard starts or stalling
  
  

• Damaged injectors and fuel pump
  
  

• Lower fuel economy
  
  

• Costly repairs — sometimes exceeding $2,000 USD
  
  

Routine maintenance not only saves money but also improves overall performance and reliability, especially for truck owners who tow or drive long distances.

Pro Tip for U.S. Truck Owners

Because diesel quality can vary across the U.S., always buy fuel from high-turnover stations. Also, consider adding a diesel fuel additive to reduce moisture buildup — particularly in cold or humid regions like the Midwest or Pacific Northwest.

In states with strict emissions standards like California, maintaining a clean fuel system also helps your truck pass annual smog checks more easily.

Real-World Insight (2025 Data)

According to a 2025 survey by Diesel Power Magazine, nearly 25% of diesel engine failures in North America are linked to fuel contamination. Trucks maintained with OEM fuel filters show 35% fewer injector issues and 10–15% better fuel economy over time.

This proves that consistent filter maintenance is one of the simplest, most effective ways to protect your 6.7 Cummins engine and maximize your truck’s lifespan.

Final Thoughts

Replacing the fuel filter 2018 Ram 2500 is one of the simplest yet most impactful maintenance tasks you can perform. It protects your 6.7 Cummins engine, improves performance, and keeps your truck running strong across U.S. terrains and climates.

A few minutes of preventive care today can save thousands in repairs tomorrow — making it one of the best investments for any diesel truck owner.

FAQs

1. How often should I change the fuel filter on my 2018 Ram 2500?
Every 15,000 miles under normal conditions, or 10,000 miles if driving in dusty or humid regions.

2. What is the OEM fuel filter part number for the 2018 Ram 2500?
Mopar 68157291AA (engine filter) and 68065608AA (chassis filter) are the official OEM parts.

3. Can I use aftermarket fuel filters instead of Mopar?
Yes, but stick to trusted brands like Fleetguard or Baldwin. Cheap filters may not meet Cummins’ filtration standards.

4. How do I know if my fuel filter is clogged?
Common signs include reduced power, hard starts, and the “Water in Fuel” warning light.

5. Does replacing the fuel filter improve performance?
Absolutely. Clean fuel improves combustion, enhances power, and helps achieve better fuel efficiency.