If you drive a diesel truck, changing the oil is one of the most important things you can do to keep it in great shape. Regular oil changes help the engine last longer, run smoother, and avoid costly repairs. 

While it might sound like something only a mechanic should do, the truth is—you can do it yourself! With a few tools and a little know-how, changing the oil in your diesel truck can be simple and satisfying.

In this guide, we’ll walk you through every step. You’ll learn how to do it safely, correctly, and confidently—even if you’ve never done it before.

Why Oil Changes Matter for Diesel Trucks

Oil is the lifeblood of your engine. It keeps everything inside running smoothly by reducing friction, cooling hot parts, and cleaning out dirt and debris. But over time, even the best oil breaks down and gets dirty. 

When that happens, your engine has to work harder, which can lead to damage.

Diesel engines especially need clean oil. That’s because they run hotter and harder than gas engines. 

They’re made for towing, hauling, and long-distance driving, so they deal with more pressure and heavier loads. This means the oil wears out faster and needs to be changed more often.

Skipping oil changes can lead to:

• Poor fuel economy
• Slower performance
• Engine damage
• Costly repairs

Doing regular oil changes helps your diesel truck run longer, cleaner, and better.

How Often Should You Change Diesel Truck Oil?

This depends on the kind of truck you drive, the oil you use, and how you drive. Here are general guidelines:

• Light-duty diesel trucks (like smaller pickups): Change oil every 5,000 to 7,500 miles.
• Heavy-duty diesel trucks (like large work trucks): Change oil every 10,000 to 15,000 miles, especially if using synthetic oil.

If you often drive in harsh conditions—like towing heavy trailers, driving on dusty roads, or idling a lot—you may need to change the oil sooner. 

Always check your truck’s owner’s manual for the manufacturer’s recommendation. It’s the best source for your exact oil type, amount, and change interval.

Tools and Supplies You’ll Need

Before starting, gather everything you’ll need. Having all your tools ready will make the job quicker and cleaner.

Here’s what you need:

• Diesel-rated engine oil (check your manual for the type and amount)
• New oil filter (exact match for your engine)
• Oil filter wrench (helps remove tight filters)
• Socket wrench and correct socket (for the drain plug)
• Oil drain pan (large enough to hold 10–15 quarts)
• Funnel (for clean pouring)
• Rags or paper towels (for cleanup)
• Gloves (optional, but keeps your hands clean)
• New washer or crush ring (for drain plug, if required)

Pro tip: Lay down cardboard or old towels under the truck to catch any drips.

Step 1: Park and Let the Engine Cool

Start by parking your truck on flat, level ground. Turn off the engine and let it cool for at least 30 minutes. Warm oil drains better than cold oil, but you don’t want it hot enough to burn you.

This is also a good time to pop the hood and check for any leaks or loose parts. Open the oil filler cap on top of the engine—this helps the oil flow out more easily when draining.

Step 2: Locate the Drain Plug

Slide under the truck and find the oil pan—a metal pan at the bottom of the engine. At the very bottom of this pan, you’ll see the drain plug, which is a large bolt.

Place your oil catch pan directly underneath the plug. Make sure it’s centered, since the oil can shoot out at an angle when first draining.

Step 3: Drain the Old Oil

Use your socket wrench to loosen the drain plug. Once it’s loose, unscrew it by hand and move your hand away quickly—oil will start pouring out immediately.

Let it drain for 10 to 15 minutes, or until it slows to just a drip. While it’s draining, inspect the oil:

• Is it super dark? That’s normal.
• Is it milky or smells like fuel? That could be a problem—have it checked.

Before moving to the next step, wipe off the drain plug and replace the washer if needed.

Step 4: Remove the Old Oil Filter

Next, locate the oil filter. It usually looks like a metal can about the size of a coffee mug. Use your oil filter wrench to loosen it, then unscrew it by hand. Be careful—some oil will likely spill out.

Make sure the old gasket (rubber ring) didn’t stick to the engine. If it did, peel it off. Leaving it behind can cause leaks when the new filter is installed.

Step 5: Install the New Oil Filter

Before putting on the new filter, dip your finger into fresh oil and rub a thin layer on the new gasket. This helps it seal better and makes removal easier next time.

Screw the new filter in by hand. Don’t use a wrench to tighten it—just turn it until it’s snug and then give it about ¾ of a turn more.

Step 6: Reinstall the Drain Plug

Once the oil has fully drained, reinstall the drain plug. Hand-tighten it first, then use your socket wrench to snug it up. Be careful not to overtighten—it just needs to be firmly secured.

Step 7: Add New Oil

Open the oil filler cap on the engine and insert your funnel. Slowly pour in the new oil. Most diesel trucks take between 10 and 15 quarts, but check your manual for the exact amount.

Pour in about 80% of the oil first, then check the dipstick before topping off. This helps prevent overfilling.

Step 8: Check the Oil Level

After pouring in the oil, wait a few minutes for it to settle. Then pull out the dipstick, wipe it clean, reinsert it fully, and pull it out again to read the level. It should be between the “Low” and “Full” marks.

If it’s low, add more oil a little at a time and check again.

Step 9: Start the Engine and Let It Run

Start your truck and let it idle for 2 to 3 minutes. Keep an eye on the oil pressure gauge and warning lights. While it runs, check under the truck for leaks, especially near the oil filter and drain plug.

After the engine runs, turn it off and wait a few minutes. Then check the oil level again and top off if needed.

Step 10: Final Check and Clean Up

Once everything looks good, tighten the filler cap and clean up any spills. Record the mileage and date of your oil change. This helps you remember when it’s time for the next one.

Also, don’t forget to safely dispose of your old oil and filter. Most auto parts stores will take used oil and filters for free. Never dump it on the ground or down the drain—it’s harmful and illegal.

Final Thoughts

Changing the oil in your diesel truck may seem like a big job, but once you do it a couple of times, it becomes second nature. It’s one of the best DIY skills a diesel truck owner can learn. 

You’ll save money, take better care of your vehicle, and feel good knowing you’re doing the job right.

Take your time, follow the steps, and enjoy the process. Your truck—and your wallet—will thank you.