How to Change Oil and Why you Should

NMT Team
Jul 1
6 min read

Every car is different, that's why if you look up a video on just "how to change oil" you probably got a little confused. Let's go over different oil changes and how to do them; then if you're interested, we'll go over why changing oil is important.

Changing Oil

Picking the correct oil

Most cars have a little label on the oil cap telling you what weight of oil, some list it in the manual, sometimes they have an oil change reminder sticker with the weight of the last oil used, or you can always ask somone at the parts store. Using the correct weight (such as 0W-20, 5W-30, etc) is incredibly important.

You'll also want to ensure you get the right amount, most cars are around 5qts, but this can differ; This information typically requires googling, or again, asking the parts guy.

Picking the correct filter

This is pretty simple; wherever you're buying your parts, ensure you get the correct filter for your vehicle and engine configuration. There's gonna be a lot of people telling you which brand to pick. As long as you're changing it regularly, this really doesn't matter, but if you want a recommendation, NMT recommends Microgard Select (only at O'Reilly), Wix, and Napa Gold (only at Napa).

Other items

If you're changing it yourself, you're gonna need a..

Drain pan
Wrench set OR Ratchet and Socket set
Oil filter removal socket (on certain vehicles)
A funnel is nice to have

Remove the oil cap

It's always good to remove this first, it will allow the oil to drain faster. If it's really tight, that can happen, and it's not a big deal to need a tool like pliers to open it.

Remove the drain plug

With the drain pan in position, remove the drain plug with the wrench or ratchet. Drain plugs are going to be on the lowest point of the engine, and is sometimes labeled "ENGINE OIL". Keep in mind, most vehicles have a transmission drain plug that can pretty easily get confused with the engine drain plug. If you see two drain plugs, the engine is always going to be closer to the front of the vehicle.

Most drain plugs range from 13mm to 19mm, but this can differ. Allow oil to drain; if the vehicle is warm, this will likely take 60 seconds; if it's cold, this can take 2 to 4 minutes.

Remove the oil filter

Here is where it can change drastically between vehicles. Let's dive in and change it two different ways.

Canister filters

If you're oil filter looks like the one pictured below (it doesn't have to be exactly alike) it's a canister filter.

Canister filters are typically located near the bottom of the engine near the drain plug, but some rare instances they're mounted at the top. Either way, they should be hand tight, but if it's too tight you can use channellocks, oil filter pliers, or an oil filter socket.

If it's one on the bottom, get the drain pan ready because it will drain from the filter itself and the area it was mounted to.

Cartridge filters

If your filter looks like the one pictured below, you have a cartridge filter; these are a bit trickier.

These will always have a cap that takes a socket or a special socket to remove, both are unfortunately rarely in a tool set.

If it's a regular socket, it's normally very large, like 22mm to 26mm.

If it's a special socket, it normally has teeth on the socket that lock into the cap, forcing you to use that specific socket. This is very common on 2004 to present Toyotas, most of these special sockets can be purchased from a local auto parts store.

These filters can be on the top or bottom. If they're on the bottom, they are typically hard to spot because they have a dirty cap covering them up. If you can't find it, look up your cars oil filter cap and look at the photos of it and then see if you can find something under the car that looks like that.

Most of these also have a giant O-Ring or gasket that goes on the cap, this needs to be replaced with every oil change and should come with the filter.

Anyway, if you got all that you need to remove the cap and remove the filter.

Replace the drain plug

Put the drain plug back in, if its still draining and its been over 4 minutes, just put it back in anyway. Some drain plugs have a copper crush washer, if so, it must be replaced, it can typically be found at a local auto parts store.

Here are some examples of a crush washer, if yours doesn't look like this then you can move on.

Reinstall oil filter

If you have a canister, just screw it back on and get it hand tight, there is absolutely no reason to use tools to tighten an oil filter.

If you have a cartridge, put the oil filter back in place, install O-Ring (after you removed the old one) and tighten the oil filter cap with the tool you used to get it off. There may be a torque specification (tightness specification), but we personally have never paid attention to that, and all our vehicles run great.

Pour in oil

Using a funnel or just pouring it straight in like an animal, whichever one suits you, pour the correct amount of oil in, most oil bottles have a little sight on the side to gauge how much you poured to make sure you're getting the right amount.

Start engine

Well, probably best to take a look underneath and make sure that oil didn't just come out the bottom, if not go ahead and start the engine.

You may hear it rattle, or even activate the oil light on some vehicles; this is normal as oil is not completely circulated yet, which usually takes about 5 seconds after the engine starts.

I normally recommend letting it run for a minute or two to ensure full lubrication and no leaks.

Why Changing Oil is Important

You’ve probably heard “you need to change your oil” more times than you can count, maybe from your dad, your mechanic, or a sticker on your windshield that’s three months past due. But why does it matter? What actually happens to oil if you don’t change it?

Let’s break it down without the filler.

What Engine Oil Actually Does

Oil isn’t just there to keep things “wet.” It’s a multi-tasking superhero inside your engine. Here's what it does:

Lubricates moving parts to reduce friction
Cools internal components by carrying heat away
Cleans by suspending dirt, carbon, and metal shavings
Seals tiny gaps between pistons and cylinder walls
Protects against rust and corrosion

Basically, oil is the one thing keeping your engine from tearing itself apart.

What Happens to Oil Over Time

Oil doesn’t last forever. Over time, it:

Breaks down from heat and pressure
Collects junk — like combustion byproducts, dirt, fuel, and metal
Thickens or becomes sludge
Loses its additives, like detergents and anti-foam agents

What Happens If You Don’t Change It

Here’s what you’re risking by skipping oil changes:

1. Sludge Buildup

Old oil thickens and turns into sludge, which clogs oil passages and sticks to engine internals. Think black peanut butter packed into every crevice of your engine.

2. Overheating

Without clean oil to reduce friction and carry away heat, parts start to run hotter than they should. Over time, this can warp metal and ruin gaskets.

3. Increased Wear

As oil loses its lubricating power, metal starts grinding against metal. You won’t hear it at first — but it’s quietly eating your engine alive.

4. Oil Starvation

If the oil gets too dirty or thick, it might not flow well — or at all. Your oil pump might not push it through the system, leading to dry spots inside the engine.

5. Complete Engine Failure

Worst-case? Spun bearings, seized pistons, or total engine lockup. At that point, an oil change won’t help — you're buying a new engine or saying goodbye to the car.

Here's a photo of a car that went over 44,000 miles without an oil change, and yes they need a new engine.

How Often Should You Change Your Oil?

Here’s a rough guide:

Driving Style	Interval
Short trips, cold starts, city driving	Every 3,000–4,000 miles
Normal mixed driving	Every 5,000 miles
Full synthetic oil & highway use	Up to 7,500 miles

Oil should not be in a car for more than 8,000 miles, and we personally think that is pushing it. 3,000 to 4,000 is the best interval for increased engine life.