Engine Oil Change Service

An oil change is the most common job in the auto trade, and it looks simple. It also carries real risk. A loose drain plug or a doubled filter gasket can empty an engine on the road and destroy it in minutes. The job rewards the person who follows the same careful routine every time. This guide covers choosing the right oil and filter, the service itself, and the checks that prove your work.

What You Will Be Able to Do

• Read an oil specification and find the correct oil and capacity for the vehicle
• Check engine oil level correctly and read what the oil is telling you
• Change oil and filter on spin-on and cartridge systems
• Avoid the common mistakes that cause leaks or engine damage
• Handle and store used oil and filters the right way

Why Oil Matters

Oil's primary job is to lubricate moving parts and reduce friction. It also carries away heat, keeps dirt in suspension, helps seal the piston rings and feeds hydraulic parts such as lifters and variable valve timing phasers. Over time heat breaks it down and contaminants build up, so it has to be replaced. The filter holds the dirt the oil collects. A used filter is full of trapped contaminants and has less capacity, so always replace it with the oil.

Choosing the Right Oil

Look up the oil in the owner's manual or service information, and check the oil cap or underhood label. Three things must match:

1. Viscosity. An oil such as 5W-30 is multi-grade. The W stands for winter. The number before it describes how the oil flows when cold, and the number after it describes its thickness at operating temperature. In 0W-20, the 0W means it flows very easily at a cold start.
2. Performance standard. In the US, look for the API donut and the ILSAC starburst or shield. API SQ and ILSAC GF-7, first licensed in March 2025, are the current gasoline categories, and they replaced API SP and GF-6 as the newest standards. A manual that calls for an older category can normally use a newer one, but check the label.
3. Manufacturer approval. Many vehicles require a specific approval, such as GM's dexos1 or a Volkswagen, BMW or Mercedes-Benz specification. An oil with the right viscosity but the wrong approval is the wrong oil, and it can affect warranty coverage.

Conventional oil is refined from crude. Synthetic oil is chemically engineered for uniform molecules, so it holds up better in extreme heat and cold. Many late-model engines require it. Do not choose by habit. Use what the vehicle calls for.

Look up the capacity for that exact engine, with filter. Capacities differ a lot between engines in the same model, so do not rely on memory.

Checking the Oil Level

1. Park on level ground.
2. Shut the engine off and wait a few minutes. About 2 minutes is typical after a hot engine stops, so oil can drain back into the pan. The owner's manual may say longer.
3. Pull the dipstick, wipe it, reinsert it fully and pull it again.
4. Read the level between the marks.

Some engines have no dipstick and show the level on the dash. Follow the manual.

While you are there, read the oil itself.

Keep the level between the marks. Too much oil is also a problem. If the level is well over full, the spinning crankshaft can whip the oil into foam. That aerated oil does not lubricate well, and the extra pressure can damage seals.

The Service, Step by Step

Before you start, confirm the vehicle's details, the oil, the filter and any open bulletins. Reminder: use the correct lift points, and lock the lift before you go underneath.

Warning: Oil from a warm engine is hot enough to burn. Wear gloves and safety glasses, and keep your arm out of the stream when the plug comes out. Exhaust parts near the plug can be hot too.

1. Warm the engine briefly. A few minutes of running is enough. Warm oil drains more completely and carries more contaminants with it.
2. Raise the vehicle and put the drain pan in position.
3. Remove the drain plug. Use the correct size wrench, and turn it counterclockwise. Some engine covers must come off first.
4. Let it drain for about 5 minutes, until the stream slows to a drip.
5. Inspect the plug and washer. Check the threads. Replace the crush washer. Crush washers deform when tightened, so reusing one risks a leak. Some plugs use a rubber seal that lasts longer, so follow the service information.
6. Reinstall the drain plug and torque it to spec with a torque wrench. Specs vary. Many Toyota oil pans call for about 27 ft-lb, and others are lower. Overtightening strips the threads, especially in aluminum, and that can mean a new pan.
7. Remove the old filter using the steps below.
8. Lower the vehicle and add oil. Start a little under the full capacity.
9. Start the engine and watch the oil pressure light. It should go out within a few seconds.
10. Check under the vehicle for leaks at the plug and filter.
11. Shut it off, wait, and recheck the level. Top up as needed.
12. Reset the oil life monitor and update the service sticker.

Warning: If the oil pressure light stays on after starting, shut the engine off immediately. Check the oil level, filter and drain plug before you restart it. Seconds without oil pressure can damage the bearings.

Spin-On Filters

1. Unscrew the old filter and let it drain.
2. Check that the old rubber gasket came off with the filter. Sometimes it sticks to the engine.
3. Wipe the mounting surface clean.
4. Apply a thin film of new oil to the new filter's rubber gasket. That lets it seal and tighten smoothly.
5. Screw it on by hand until the gasket touches, then tighten as the filter maker says, usually about three-quarters of a turn.

This gasket check is the most important step in the job. If the old gasket stays on the engine and the new filter goes on over it, you have a double gasket. It cannot seal, and oil pressure can blow it out and dump the oil in seconds.

Cartridge Filters

Many engines use a replaceable paper element inside a housing.

1. Remove the cap with the correct socket. Let the oil drain back first if the housing has a drain.
2. Pull out the old element and note how it sits.
3. Replace the O-ring with the new one from the kit, and lubricate it with fresh oil.
4. Install the new element and torque the cap to spec.

Warning: Top-mounted plastic cartridge housings crack if overtightened. Use a torque wrench, not an impact gun. A cracked housing is a major leak.

Handling Used Oil and Filters

Used oil is regulated. Federal rules at 40 CFR Part 279 cover how shops store and recycle it, and states add their own.

• Store used oil in a closed container or tank labeled "Used Oil".
• Never mix used oil with solvents, brake cleaner, coolant or fuel. Used oil containing solvents can count as hazardous waste, and that makes the whole tank a costly problem.
• Drain filters before they go in the filter bin, and follow your shop's and state's rules.
• Clean up spills right away with absorbent, and keep oil out of floor drains.

Used oil can irritate skin. Wash your hands, and use nitrile gloves if your shop supplies them.

Add-On Checks

An oil change is the moment to catch small problems.

• Engine air filter. Light dust is fine. If it is packed with dirt or leaves, recommend a new one, since a restricted filter can reduce power.
• Cabin air filter. It is usually behind the glove box. A clogged one causes weak airflow, musty smells and windows that will not clear.
• Washer fluid. Top it up, using a winter blend where it freezes. Running a washer pump dry can damage it.
• Other fluid levels, tires, lights and wipers. Follow your shop's inspection sheet.

Common Mistakes

Check Your Understanding

1. A customer's manual calls for 0W-20 with a dexos1 approval. You have a 0W-20 oil with no dexos1 mark. Can you use it?
2. You spin off the old filter and do not see its rubber gasket. What do you do?
3. You start the engine after a service and the oil light stays on. What is your next move?
4. A coworker asks you to pour leftover brake cleaner into the used oil tank. What do you say?

Answers

1. No. The viscosity is right, but the approval is missing. Find an oil with the required approval.
2. Stop and check the engine's mounting surface. The gasket is probably stuck to it. Remove it before you install the new filter.
3. Shut it off immediately. Check the oil level, the filter and the drain plug before restarting.
4. No. Mixing solvents into used oil can turn the whole tank into hazardous waste.

Key Takeaways

• Match viscosity, performance standard and manufacturer approval, and look up the capacity for the exact engine.
• Check for the old filter gasket every time. A double gasket can empty the engine in seconds.
• Torque the drain plug and cartridge cap, and replace the crush washer.
• If the oil light stays on after starting, shut the engine off immediately.
• Milky oil means coolant may be in the engine, so report it.
• Keep used oil clean of solvents, and store it in a labeled, closed container.