What you need to do before you start an oil change on a GMC

Before you drain the old oil, gather your supplies and locate three things under your GMC: the oil drain plug, the oil filter, and the oil fill cap on top of the engine. You will need new oil (the weight and amount depend on your specific GMC model and year — check your owner's manual or the sticker inside the driver's door jamb), an oil filter that matches your vehicle, a drain pan, a wrench or socket to fit your drain plug, and an oil filter wrench or strap wrench to remove the old filter.

Park on level ground, let the engine cool for at least five minutes (warm oil drains faster, but hot oil can burn you), and engage the parking brake. If your GMC sits low to the ground, you may need to raise it with a jack and find it on jack stands — never work under a vehicle supported only by a jack. Some GMC models have plastic undercarriage panels that must be removed first to reach the drain plug; your owner's manual shows whether yours does.

Key Takeaways

  • The oil drain plug is located on the bottom of the engine pan, and you will need a wrench sized to fit it — common sizes are 13mm, 15mm, or 17mm depending on your GMC model year.
  • Drain the old oil into a pan, replace the drain plug and tighten it by hand first, then use a wrench to snug it without over-tightening, which can strip the threads.
  • The oil filter screws on by hand and should be replaced every oil change; fill it about three-quarters full with new oil before installing it, then hand-tighten it until the rubber gasket touches the engine, then turn it one more half-turn.
  • After adding new oil through the top fill cap, wait a minute for it to settle into the pan, then check the level with the dipstick or electronic gauge to confirm you have added the correct amount.
  • Start the engine and let it run for 30 seconds to circulate the new oil, then turn it off, wait a minute, and check the level again to make sure it is in the correct range.

Draining the old oil and replacing the drain plug

Position your drain pan directly under the drain plug. Using the correct wrench size, turn the plug counterclockwise until it is loose enough to unscrew by hand. Finish unscrewing it by hand, but be ready — the oil may still be warm. Let the oil drain completely into the pan; this usually takes five to ten minutes. While you wait, inspect the drain plug for damage. If the threads are stripped or the plug is bent, you will need a new one before you reinstall it.

Once the oil has stopped dripping, wipe the drain plug clean with a rag and inspect the rubber or metal gasket on the bottom. If it looks cracked or flattened, replace it with a new one (some drain plugs come with a new gasket, others require you to buy one separately). Screw the plug back in by hand first to avoid cross-threading, then use your wrench to tighten it. Tighten firmly but do not over-tighten — you are aiming for snug, not maximum force. A typical drain plug torque is 15 to 25 foot-pounds, though your manual will specify the exact number for your GMC model.

Removing and installing the oil filter

Locate the oil filter, which is usually a cylindrical canister on the side of the engine. Position your drain pan underneath it to catch the oil that will spill when you remove it. Using an oil filter wrench or strap wrench, turn the filter counterclockwise until it is loose, then unscrew it by hand. Expect about a quart of old oil to pour out. Set the old filter aside — you will need to dispose of it at a recycling center or auto parts store, many of which take used filters for free.

Before you install the new filter, open the new one and pour about three-quarters of a quart of fresh oil into it. This pre-fills the filter so that when the engine starts, it does not run dry for a moment while oil flows through. Wipe the filter mounting surface on the engine clean with a rag. explore a thin layer of new oil to the rubber gasket on the new filter — this helps create a good seal and makes removal easier next time. Screw the new filter on by hand until the gasket touches the engine, then turn it an additional half-turn. Do not use a wrench; hand-tight is correct.

Adding new oil and checking the level

Locate the oil fill cap on top of the engine — it usually has an oil can symbol on it. Unscrew it and set it aside. Pour the new oil slowly into the opening. The amount you need depends on whether you are doing a filter change (which requires more oil) or just topping off. Your owner's manual or the oil bottle label will tell you the total capacity. Start by adding about three-quarters of the recommended amount, then check the level before adding the rest.

Wait one minute for the oil to drain down into the pan, then check the level using either the dipstick or the electronic oil level gauge, depending on which your GMC has. On a dipstick, pull it out, wipe it clean, reinsert it fully, then pull it out again and read the level — it should be between the minimum and maximum marks. On an electronic gauge, turn the ignition to the "On" position without starting the engine and read the display. Add oil in small amounts until the level is correct, then replace the oil fill cap.

Starting the engine and final checks

Start the engine and let it run for about 30 seconds. This circulates the new oil through the engine and filter. Turn off the engine and wait one minute for the oil to settle back into the pan. Check the level again using the same method you used before. The level should still be in the correct range. If it is low, add a small amount more and recheck.

Once the level is correct, you are done. Dispose of the old oil at a recycling center, auto parts store, or municipal hazardous waste facility — never pour it down a drain or into the ground. Keep a record of the date and mileage of your oil change so you know when the next one is due. Most GMC vehicles need an oil change every 5,000 to 10,000 miles, though newer models with synthetic oil may go longer; your owner's manual specifies the interval for your year and model.

Common mistakes that damage your engine

The most common error is over-tightening the drain plug or filter. Both have rubber gaskets that seal when snug, and tightening harder does not improve the seal — it only strips the threads or cracks the gasket, causing leaks. Tighten the drain plug until it is snug, then stop. Tighten the filter until the gasket touches, then turn it one more half-turn and stop.

Another frequent mistake is forgetting to check the oil level after the first start. The new filter holds oil that was not in the pan before, so the level will be higher than you expect. If you do not check, you may think you need to add more and overfill the engine, which can damage the engine and trigger warning lights. Always check after the engine has run and settled.

Finally, do not reuse the old drain plug gasket or skip pre-filling the new filter with oil. A flattened gasket will not seal, and a dry filter can starve the engine of oil for a few seconds on startup. Both are cheap to prevent and expensive to repair.

Frequently Asked Questions

What oil weight should I use in my GMC?

The correct weight is listed in your owner's manual and on a sticker inside the driver's door jamb. Common weights for GMC trucks and SUVs are 5W-30 or 0W-20, but it varies by engine size and year. Using the wrong weight can reduce fuel economy or cause engine wear. If you are unsure, ask at an auto parts store with your vehicle's year, make, and model.

Can I change the oil without raising the vehicle?

It depends on your GMC's ground clearance. Trucks and larger SUVs usually have enough clearance to slide under without lifting. Smaller or lowered vehicles may need to be raised. If you cannot fit under safely, use a jack and jack stands — never work under a vehicle supported only by a jack.

How do I know which oil filter fits my GMC?

The filter part number is in your owner's manual, or you can look it up online using your vehicle's year, make, model, and engine size. Auto parts stores can also cross-reference the filter if you give them that information. Using the wrong filter can cause leaks or poor oil flow.

What should I do with the old oil?

Take it to a recycling center, auto parts store, or municipal hazardous waste facility. Many auto parts stores accept used oil for free. Never pour it down a drain, into the ground, or into the trash — it contaminates water and soil.

How often should I change the oil in my GMC?

Most GMC vehicles need an oil change every 5,000 to 10,000 miles, though newer models with synthetic oil may go 7,500 to 10,000 miles or longer. Check your owner's manual for the exact interval for your year and model, and keep records of when you change it so you do not miss a service.