Modern oils are significantly better at lubricating and remaining stable than oils of old. This has been a necessity to cope with the increasing precision and efficiency of modern engines.  

Service intervals, therefore, have increased for most manufacturers. In this article we’ll take a look at when you should be changing your oil and why.  

What does oil actually do in an engine? 

In all engines, there are many points at which metal parts rub against each other. The most prominent instance of this in a car engine is the piston running up and down inside the cylinder.  

Oils coat the surfaces in a film, which drastically reduces friction. This reduction in friction both reduces wear on the components and also reduces the amount of heat produced. 

High performance engine oils reduce friction even further, prolonging parts and increasing efficiency. The engine oil is pumped around the engine, and flows through various pipes built into the engine block, it helps lubricate every part from the camshafts down to the main bearings.  

What is Synthetic Oil and do I need it? 

Most modern cars require fully synthetic oil, which is ultra-processed and performs much better than semi-synthetic or non-synthetic oils.  

Many manufacturers of modern vehicles advise using fully synthetic oils, this is because the engines have been designed with high tolerances, so to ensure you’re giving your car the best care, use the recommended oil, which is usually specified in the manual. 

What is the benefit of changing my engine oil? 

There are several reasons why changing engine oil is recommended, the foremost being that oil degrades over time. The bonds that chemically create the oils viscosity and lubricating properties are not invulnerable to heat and time.  

An engine could easily be running at operating temperature for 150 hours between oil changes. Any reduction in lubrication and protective properties through the oil is not welcomed, and is easily remedied by changing the oil for fresh.  

The cost of rebuilding an overly worn engine, especially one that has not had proper lubrication, will be far more expensive than changing the oil on the correct schedule. 

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Oil is therefore a cheap consumable that increases the life of an engine. 

Engine oil also absorbs all the soot from fuel combustion that makes its way into the oil chambers, this is what turns the oil black, along with oxidisation. 

This blackening of the oil is typically reducing the quality also, and as the previous point, will increase wear on your engine.  

Another reason for replacing oil is that when engine parts wear together, microscopic amounts of metal are removed from the components. Many of these particles become trapped in the sump; the oil reservoir at the bottom of the engine. 

Whilst the oil pump has a filter attached to the inlet pipe, to catch larger debris, smaller particles may still make their way through the engine causing significant extra wear.  

What will happen if I don't change my oil? 

Sometimes life gets in the way of car maintenance, but for the sake of future repairs, it’s best to prioritise keeping your car serviced.  

The engine will wear much faster 

As we’ve discussed, engine oil lubricates and prevents wear to the engine. It also breaks down over time and with the heating and cooling cycles of daily use. If you don’t change your oil after the recommended number of miles, it will wear quicker.  

This will have an even bigger impact if the car is a few years old now, or has done significant mileage of over 100,000 miles. All the components will have been experiencing wear for many hours and will need to be lubricated properly in order to run smoothly.  

With that being said, don’t use the fact your car is newer to avoid servicing: 

Its value will reduce 

Servicing is a top priority for used car buyers. If your car is missing service stamps, or the services have not been completed at all, you will put off many serious buyers when you come to sell it. 

Many dealerships will also reduce your part-ex value significantly, as patchy service history will affect their resale value also.  

You might be required to by your finance agreement 

If your car is on a lease, HP or PCP finance deal, you may be bound by the terms of the agreement to keep up to date with the required service intervals.  

This is mainly due to the fact that most finance deals other than hire purchase, allow you to return the car at the end of the agreement. 

It helps identify other issues 

When your car is serviced, the technician will need to put your car on a lift. In doing this as well as changing the oil filter, they may be able to notice small issues that would otherwise go unnoticed. 

These issues can often turn into unexpected and expensive problems later on, if not dealt with promptly. 

Another way the engine's health can be inspected is through the oil that comes out of it. The condition of the old engine oil can tell a lot about the state of the engine. If the oil is overly dark it could indicate overheating. If it’s very thin or smells of petrol piston rings or other sealing components could have failed and more. If you get to this stage, you might want to take your car to the mechanic.

Intervals  

It's clear then that engine oil is vital, and should not be left to degrade to the point where it no longer functions properly. So what oil change intervals should you be following? 

Whilst modern cars use advanced oils, the tolerance and precision of the engine is such that they often still require just as frequent oil changes. 

Manufacturers such as Toyota, Honda, Ford, Hyundai and Nissan all recommend intervals of between 5,000 and 8,000 miles. Audi, BMW and Mercedes vehicles often have a slightly longer interval of up to 10,000 miles, known for their reliable status. 

For the most accurate method of determining when to change your oil, check your owner's manual for specific recommendations for interval and oil type.  

Many cars now also have a service light or system built into the car's onboard infotainment system, which can often determine depending on the driving conditions as well as mileage. 

Is your next service due? 

Enter your registration and postcode to apply for interest-free monthly payments for repairs and to see a list of local dependable garages and dealerships signed up to Bumper. 

Once you’ve completed your application, you’ll be given a credit limit of up to £5,000 (depending on which garage you want to go to) and a unique code. 

Contact the garage to get booked in. Let them know you want to pay using Bumper and once the work is completed present them with your unique code. They’ll sort the rest.

Author - Joseph Law

Joseph has been writing about cars for over seven years and writing for Bumper for over two, blending his passion for automobiles with a talent for storytelling.

Joseph has written about engineering and cars for Autozilla, Komaspec, and several engineering manufacturers. When he's not writing or tinkering with one of his five cars, Joseph dreams of owning an Alfa Romeo 33 Stradale.