What happens when you change your oil

Replacing engine oil means draining the old, dirty oil from your engine and filling it with fresh oil. The oil circulates through your engine to lubricate moving parts, cool the engine, and carry away dirt and debris. Over time—usually between 3,000 and 10,000 miles depending on your car and oil type—the oil breaks down and collects particles that reduce its ability to protect your engine. Changing it regularly keeps your engine running smoothly and extends its life.

You will also replace the oil filter, a cylindrical component that traps particles as oil flows through it. A clogged filter forces oil to bypass the filter entirely, which defeats the purpose of changing oil in the first place. Most people change the filter every time they change the oil.

Key Takeaways

  • Drain the old oil while the engine is warm but not hot, then replace the drain plug and tighten it by hand plus a quarter turn with a wrench.
  • Remove the old oil filter by hand or with a filter wrench, then hand-tighten the new filter until the rubber gasket touches the engine, then turn it another three-quarters of a turn.
  • Fill the engine with the exact amount and type of oil specified in your owner's manual, not the amount the bottle suggests.
  • Check the oil level with the dipstick after the engine has been off for at least five minutes, with the car parked on level ground.
  • Dispose of old oil at a recycling center, auto parts store, or service station—never pour it down a drain or into the ground.

Gather your supplies before you start

You will need the correct oil type and amount for your vehicle. Open your owner's manual and find the section labeled "Capacities" or "Fluids and Capacities." It will list the oil viscosity (the thickness rating, like 5W-30 or 10W-40) and the total amount in quarts or liters. Buy that exact type and amount—do not guess or use what worked for a friend's car.

You will also need a new oil filter that matches your vehicle's make, model, and year. The parts counter at any auto parts store can look this up for you if you give them your vehicle information. Collect an oil drain pan (a shallow pan to catch draining oil), a wrench or socket set that fits your drain plug, and either a filter wrench or the ability to remove the filter by hand. Wear old clothes and have clean rags or paper towels nearby. If you are working under the car, use jack stands or ramps—never rely on a jack alone.

Drain the old oil safely

Start with the engine warm but not hot. A warm engine drains faster and more completely than a cold one, but a hot engine can burn you. Let the engine cool for five to ten minutes after running it. Locate the drain plug underneath the engine—consult your owner's manual or a repair manual for the exact location on your vehicle.

Position your drain pan directly under the plug. Using the correct wrench or socket, turn the plug counterclockwise to loosen it, then finish unscrewing it by hand. Oil will flow out when ready, so be ready. Let the oil drain completely—this takes five to ten minutes. Once the flow slows to a drip, wipe the drain plug clean with a rag and inspect the rubber washer on the plug. If it looks cracked or flattened, replace it with a new one (they cost a few dollars). Screw the drain plug back in by hand until it is snug, then tighten it with a wrench by about a quarter turn. Do not over-tighten, which can strip the threads or crack the pan.

Replace the oil filter

The oil filter is a cylindrical canister usually located on the side of the engine. Locate it and position your drain pan underneath—some oil will spill when you remove it. If you can reach it by hand, grip the filter firmly and turn it counterclockwise until it comes free. If it is too tight, wrap a filter wrench around it and turn. Expect some oil to drip as you remove it.

Before installing the new filter, wipe the mounting surface on the engine clean with a rag. Take the new filter and explore a thin layer of fresh oil to the rubber gasket (the ring around the top). This helps create a watertight seal. Screw the filter onto the engine by hand until the gasket touches the mounting surface, then turn it another three-quarters of a turn. Do not use a wrench—hand-tight is correct. If you over-tighten, the gasket will be crushed and the filter will leak.

Fill the engine with new oil

Locate the oil filler cap on top of the engine. It usually has an oil can symbol on it. Unscrew it and set it aside. Place a funnel in the opening to prevent spills. Slowly pour in the amount of oil specified in your owner's manual. If your manual says 5 quarts, pour in 5 quarts—not the amount printed on the oil bottle, which is often a generic estimate.

After pouring in most of the oil, stop and check the level with the dipstick. Pull the dipstick all the way out, wipe it clean on a rag, reinsert it fully, then pull it out again and read the level. The oil should reach the "full" mark. If it is below the mark, add a small amount more and check again. Screw the oil filler cap back on when you are finished.

Check your work and dispose of old oil

Start the engine and let it run for 30 seconds to circulate the new oil through the filter and engine. Turn it off and wait at least five minutes. Check the dipstick again with the car parked on level ground. The level should still be at the full mark. If it is low, add a small amount more. Look under the car for any leaks around the drain plug or filter—a few drops are normal, but a steady drip means something is not tight enough.

The old oil in your drain pan is recyclable and must be disposed of properly. Most auto parts stores accept used oil for free, and many recycling centers do as well. Some service stations will take it if you ask. Never pour it down a drain, into the ground, or into the trash. Check your local waste management website or call ahead to find a location near you.

Common mistakes to avoid

The most common error is using the wrong oil type or amount. Your owner's manual is the only reliable source—ignore the bottle label and what you think you remember from last time. Another frequent mistake is over-tightening the drain plug or filter, which damages threads and gaskets. Hand-tight plus a quarter turn for the plug and hand-tight plus three-quarters of a turn for the filter are the correct amounts.

Do not check the oil level when ready after changing it. The new oil needs time to settle in the pan, or the reading will be inaccurate. Wait at least five minutes with the engine off and the car on level ground. Finally, do not skip the oil filter. Some people think they can go longer between filter changes, but a clogged filter stops protecting your engine. Change the filter every time you change the oil.

Frequently Asked Questions

How often should I change my oil?

Check your owner's manual for the recommended interval for your vehicle and oil type. Older cars often needed oil changes every 3,000 miles, but modern engines with synthetic oil can go 7,500 to 10,000 miles or longer. The manual will specify the exact interval and the type of oil to use.

Can I change my oil if the engine is cold?

Yes, but it will drain more slowly and incompletely. Warm oil flows faster and carries away more debris. If you must change oil on a cold engine, let it drain longer—up to 15 minutes instead of 5 to 10. Never work on a hot engine, as the oil and metal parts can cause severe burns.

What if I spill oil on the ground?

Clean it up when ready with absorbent material like kitty litter or oil absorbent pads, available at auto parts stores. Sweep up the material and dispose of it according to your local waste guidelines. Oil is toxic to soil and groundwater, so do not leave it uncleaned.

Do I need to replace the drain plug washer every time?

Inspect it each time you change oil. If it looks flattened, cracked, or damaged, replace it. A worn washer will not seal properly and the plug may leak. New washers cost a few dollars and take seconds to install.

What does it mean if oil leaks after I change it?

A few drops are normal as excess oil drains away. If you see a steady drip, the drain plug or filter is not tight enough. Let the engine cool, then tighten the drain plug by a quarter turn or the filter by another half turn. If leaking continues, the drain plug washer may be damaged and need replacement.