A car’s maintenance, especially oil changes, can be easy to forget about. Every day, we jump in and out of our automobiles and trust everything will run as it should. In this article, we explain what happens if you don't change your oil.

What happens if you don’t change your oil?

Not changing your engine oil will lead to increased wear, worse MPG and can even contribute to engine failures.

The oil in your engine reduces friction and heat by lubricating the moving parts. When the oil is fresh, it lubricates at peak efficiency and minimises wear on the engine components.

When the oil breaks down, the two faces will begin to wear significantly faster. This will be hard to notice on the camshafts, but over time this increased wear on the cylinder bores will create a significant loss in power.

Overheating

Not only does oil lubricate, but it also plays a crucial role in cooling down certain parts of the engine. Race cars often have dedicated oil coolers, but many run-of-the-mill cars also implement designs to reduce oil temperature. 

Surpassing oil change intervals can lead to both a reduction in oil-based cooling as well as excessive heat from increased friction. 

Both symptoms are not good for an engine, more heat generally equates to less efficiency, more wear and a higher chance of something breaking permanently.

Reduced fuel efficiency

Not changing your oil on time could increase your fuel consumption. As a consequence of the increase in heat, reduction in compression due to worn cylinders and a lack of cooling, fuel efficiency will likely decrease.

Over time this could amount to a significant increase in fuel costs, probably more so than the cost of an oil change!

Increased emissions 

A decrease in fuel efficiency generally coincides with an increase in harmful emissions, particularly through the burning of oil due to excessive engine wear. 

A small amount of engine oil will always make its way into the engine's combustion chamber, but the more wear to the cylinder walls, the more will enter, and burn off as nasty emissions. 

Systems will clog with dirt and debris

There are many complex mechanisms that rely on good oil flow to function properly. Examples include variable valve timing, turbochargers and engine breathers.

VVT or Vanos systems often use the engine's oil pressure to operate. These are extremely precise systems, and any decrease in oil pressure, quality or viscosity can affect them. Best case, the engine stops varying the valve timing properly. 

Worst case the Vanos system clogs and requires removal and replacement or cleaning.

Turbos can fail and destroy your engine

Extremely common on modern cars, turbochargers utilise waste energy from the exhaust to increase power and efficiency, turbos are responsible for the modern spate of small, high MPG-achieving engines such as those found in Ford, Audi and Volkswagen vehicles. 

Turbos spin incredibly fast, in excess of 10,000 RPM. To spin efficiently they need a strong supply of oil, a partial or momentary pause in the supply of oil can cause the turbine to overheat and fail.

Because half of the turbo is in the path of air entering the engine, if shards of the turbine break off due to catastrophic failure, they can easily enter the engine, causing serious damage. 

Worse performance

If you’ve ever waited a long time between oil changes, you probably noticed a difference in how well the car performed after the oil change was complete. Simply put, with fresh new oil, your engine’s spinning parts can move smoothly and use less power to make their revolutions. 

Voiding your warranty 

The manufacturer’s warranty for a new car can last as long as a decade — if you stick to its prescribed maintenance schedule. Skip too many oil changes and the terms of the warranty might render it void. 

If there’s ever a major repair it could cost you thousands more than it would have if the warranty was still valid. 

Reduced resale value 

Resale value probably isn't the first thing on your mind when you buy a car. Eventually, however, the day comes when you want to sell or trade in your car for a new one. 

Keeping to a schedule of regular oil changes will increase your car's resale value. On inspection or in a test drive the engine will perform noticeably better. Keep a detailed record of oil changes and other regular maintenance; you might even improve your sale price. 

What are the benefits of changing your oil on schedule?

Keeping your engine healthy with fresh oil has many benefits, including preventing engine failure, reducing engine wear, increasing resale value and generally improving your car maintenance as a whole. 

Catching other problems early 

When you have an oil change done it gives the mechanic an opportunity to visually inspect your car under the bonnet. They'll see the battery, air filters, brakes and whatever else they have on their standard list. That means they’ll be able to note any potential problems before they happen.  

It helps you keep to a schedule 

Every car has a suggested manufacturer’s maintenance schedule for regular servicing. Focusing on oil changes makes it easier to track the intervals and ensure you’re being seen by a mechanic at least once a year. 

Your mechanic will probably remind you about any upcoming scheduled maintenance in addition to the oil change, so you can book an appointment on the spot. 

Stopping catastrophes from happening 

If your engine oil turns to sludge, it won't be able to lubricate anymore, and your car engine will seize up. That means the metal parts fuse together under intense friction and heat. It's almost impossible to fix, probably requiring a new engine or even a write-off of the car.

Does missing oil changes cause engine wear?

Yes, oil prevents wear by minimising the friction between the moving parts of the engine. Oil also only has a limited service life, meaning it breaks down and stops providing the same level of lubrication, leading to rapid wear. 

Who can change my oil?

Almost anyone can do an oil change. The tools needed to change your car’s oil are not complex or expensive, but it does need to be done safely, as it usually requires jacking up the vehicle and crawling under the engine.

If you don’t want to change it yourself, you should be able to easily find a garage for an oil change near you. Almost any garage can offer oil changes as it is one of the most basic tasks a mechanic can do. 

Split the cost of repairs into interest-free monthly repayments and choose from thousands of service partners nationwide. 

Is my oil changed during a service?

As one of the most important elements of servicing on a car, oil changes are always included in interim and full services. This generally also includes an oil filter change, to keep the new oil cleaner for longer.

It’s good practice to check what oil grade and quality the garage will be using, especially if you’re not taking your car to a main dealer for servicing, we have a handy guide on oil grades here.

Is my oil changed during an MOT test?

Whilst things like engine oil leaks would be noticed, the MOT test does not include an oil level or quality check, nor does it include an oil change. It’s a good idea to book a service at the same time as an MOT test for this reason. 

For cars more than three years old, an annual MOT test is a legal requirement. The test includes the checking of all safety critical systems such as brakes, suspension and tyres. 

For more on exactly what an MOT covers, check out our guide here.

Is it okay to go a year without an oil change?

Put simply, no. For most cars, the oil should be changed every 3-6,000 miles. This means for most cars not changing your oil for over a year means missing two separate changes which could seriously damage your engine.

Making time for something as mundane as an oil change can seem like a nuisance, but they are vital to your car’s healthy operation. If you want your car to last a long time and to perform well, take the time to get the oil changed. If you don't, expect to spend more.

What are the signs that suggest an oil change?

Over time, the engine will start to exhibit common signs that you need an oil change, like increased fuel consumption, reduced performance and a smokey exhaust fume.

The danger appears because unlike knocking suspension or a blowing exhaust, not changing the oil does not make a loud or easily noticeable difference, at least for the first few months. 

However, once these symptoms start to show, it may well mean your engine is seriously damaged already - so make sure to follow those service intervals!

How many miles can you go over an oil change sticker?

You might find a sticker inside your engine bay that states a mileage, these are often used to record when an oil change was last done. It’s best to limit the miles past the sticker by as much as possible, even having the oil change done in advance.

The trouble with oil change stickers is that they might not be 100% accurate, as there is no way to officiate the work.

We generally recommend using your car's service book, that way there can be no confusion over what was done and by whom. The book can also be passed over to a prospective buyer, giving a detailed history of the car.

What happens if you don't change your oil for 10,000 miles?

Some manufacturers now recommend an oil change every 12-15,000 miles, so it may well be that 10,000 is fine. But as the previous point, it's best to check your owner’s manual alongside the service records for peace of mind. 

Need an expert opinion? Book your vehicle in with a reliable repairer and split the cost into monthly payments, completely interest-free.