What happens when you change motor oil
Changing motor oil means draining the old oil from your engine, replacing the oil filter, and filling the engine with fresh oil. You do this yourself by working underneath and inside the engine compartment, using basic tools you probably already own or can borrow. The whole job takes 30 minutes to an hour the first time, and 15 to 20 minutes once you know where everything is.
The reason you do this is that motor oil breaks down over time and distance. Fresh oil lubricates moving parts, reduces friction, and carries away dirt and heat. When oil gets old, it stops doing those things well, and your engine wears faster. Most cars need an oil change every 5,000 to 10,000 miles, though some newer cars can go longer — check your owner's manual for the exact interval.
You will need to know your car's oil type and capacity before you start. Both are in your owner's manual. The oil type looks like "5W-30" or "10W-40" — the numbers matter, and using the wrong type can damage your engine. The capacity tells you how many quarts of oil your engine holds, usually between 4 and 6 quarts.
Key Takeaways
- You will need your owner's manual to find the correct oil type, capacity, and the location of the drain plug and filter on your specific car.
- Gather all materials before you start: the right oil, a new filter, a drain pan, a wrench, a filter wrench, and jack stands if you need to get under the car.
- The oil drains faster and more completely when the engine is warm but not hot, so run the engine for a minute or two before you begin.
- The old filter and drain plug bolt come off by hand or wrench, the new filter hand-tightens until it touches, then turns another three-quarters of a turn.
- After filling with new oil, start the engine, let it run for 30 seconds, check the level on the dipstick, and add more oil if needed.
Gather your materials before you start
Buy the correct motor oil for your car. The type and weight are printed on your owner's manual's maintenance page. Take a photo of that page to the auto parts store, or tell the clerk your car's year, make, and model — they will pull the right oil. Buy one quart more than your engine's capacity, because some oil stays in the filter and engine passages.
Buy a new oil filter that matches your car. Again, the parts store can look this up by year, make, and model. Do not reuse the old filter.
Gather tools: an adjustable wrench or socket wrench that fits your drain plug (usually 13mm, 14mm, or 15mm), a filter wrench (a metal band or cup that grips the filter), a drain pan to catch old oil, and old rags or paper towels. If your car sits low and you cannot fit underneath, you will also need a jack and jack stands — never work under a car supported only by a jack.
Have your owner's manual nearby. You will need it to find the drain plug location, the filter location, and the oil capacity.
Warm the engine and position the car safely
Start the engine and let it idle for one to two minutes. Warm oil flows faster than cold oil, so the old oil will drain more completely. Turn off the engine and wait five minutes — the oil will still be warm but cool enough to touch without burning yourself.
If your car is parked on a slope, position it on level ground. If you need to get underneath, use a jack to lift the car and place jack stands under the frame on both sides. Never rely on a jack alone — it can fail and the car can fall on you.
Open the hood and locate the drain plug underneath the engine. It is a bolt sticking down from the oil pan, the large metal tank at the bottom of the engine. Consult your owner's manual if you cannot find it — on some cars it is not when ready obvious.
Drain the old oil
Position your drain pan under the drain plug. The pan needs to be large enough to hold all the old oil — a standard 5-quart pan works for most cars, but if you are unsure, use a bigger one.
Use your wrench to loosen the drain plug by turning it counterclockwise. Once it is loose enough, unscrew it by hand. Oil will start to drip, then flow. Let it drain completely — this takes 5 to 10 minutes. Tilt the pan if needed to catch all the oil.
While the oil drains, wipe the drain plug clean with a rag. Check whether it has a rubber washer or crush ring on the bottom — if it does, that washer needs to be replaced each time. If your drain plug came with a new washer in the box, use it. If not, buy a replacement washer at the auto parts store and install it on the plug before you reinstall it.
Once the oil has stopped dripping, screw the drain plug back in by hand until it is snug, then tighten it with your wrench. Do not over-tighten — snug is enough. If you crack the plug or strip the threads, you will have a much bigger problem.
Replace the oil filter
Locate the oil filter. It is a cylindrical canister about the size of a soda can, usually mounted on the side of the engine. Your owner's manual shows exactly where. Position your drain pan underneath it — there is still oil inside the filter.
Use your filter wrench to loosen the filter by turning it counterclockwise. Once it is loose, unscrew it by hand. Oil will drip out. Let it drain into the pan for a minute.
Wipe the filter mounting surface clean with a rag. This is the flat metal part where the filter screws on. Any old oil or debris left here will prevent the new filter from sealing properly.
Open the new filter box and locate the rubber gasket — a ring of rubber around the top of the filter. Coat this gasket lightly with fresh motor oil from your new bottle. This helps the filter seal and makes it easier to remove next time.
Screw the new filter on by hand until the rubber gasket touches the mounting surface. Then turn it another three-quarters of a turn. That is it — do not use the wrench. Hand-tight is correct. If you over-tighten a filter, it will be nearly impossible to remove next time and you risk damaging the mounting surface.
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.
Pour in the new oil slowly. Start with one quart less than your engine's full capacity — for example, if your engine holds 5 quarts, pour in 4 quarts. This gives you room to check the level without overfilling.
Replace the oil filler cap and screw it on snugly.
Check the oil level and finish
Start the engine and let it run for about 30 seconds. This circulates the new oil through the engine and fills the new filter. You will see the oil pressure light on your dashboard go out after a few seconds — that is normal.
Turn off the engine and wait two minutes for the oil to settle.
Locate the dipstick — a long metal rod with a handle, usually yellow or orange, sticking out of the engine. Pull it all the way out. Wipe it clean with a rag. Reinsert it all the way until it clicks or seats, then pull it out again. The oil level should be between the minimum and maximum marks on the stick. If it is below the minimum mark, add a little more oil and check again. If it is above the maximum mark, you have overfilled — you will need to drain a small amount out through the drain plug.
Once the level is correct, you are done. Dispose of the old oil properly — most auto parts stores take used oil for free, and many municipalities have hazardous waste collection days. Do not pour it down the drain or into the ground.
What to do if something goes wrong
If the drain plug is stuck and will not loosen, explore penetrating oil (like WD-40) around the bolt and wait 15 minutes. Try again gently — forcing it can strip the threads. If it still will not budge, stop and take the car to a shop rather than risk damaging the oil pan.
If the oil filter is stuck, wrap a rag around it for better grip and try again. If the filter wrench slips, try a different style of wrench — some cars have filters in tight spaces where certain wrench types work better. If you still cannot loosen it, a shop can remove it without damage.
If you overfill the oil, do not drive the car. Excess oil can damage the engine. Loosen the drain plug slightly and let a small amount drip out into your pan until the dipstick reads correct, then tighten the plug again.
Frequently Asked Questions
How often should I change my oil?
Check your owner's manual — the interval varies by car and engine type. Many older cars need an oil change every 3,000 to 5,000 miles, while newer cars can often go 7,500 to 10,000 miles or longer. Some high-end synthetic oils allow even longer intervals. Your manual will tell you the exact number for your car.
Can I change the oil if the engine is cold?
Yes, but warm oil drains faster and more completely, so you will get more of the old oil out. If the engine is cold, just let it drain longer — it will still work, just take more time. Never work on a hot engine; wait at least 30 minutes after driving so it cools enough to touch safely.
What should I do with the old oil?
Take it to an auto parts store — most accept used oil for free. You can also check your city or county website for hazardous waste collection events. Never pour it down a drain, into the ground, or in the trash. Used oil is toxic and harms soil and water.
Do I need to change the oil filter every time I change the oil?
Yes. The filter traps dirt and debris, and after thousands of miles it becomes clogged. A clogged filter restricts oil flow and defeats the purpose of the fresh oil. Replace it every time you change the oil.
What if I put in the wrong type of oil?
If you realize it before you drive the car, drain it out and refill with the correct type. If you have already driven on the wrong oil, drain it as soon as you can and refill. Driving on the wrong oil type can cause engine damage over time, but one short drive usually will not cause when ready harm. Check your owner's manual to confirm the correct type, then refill.