What Happens if You Don't Get an Oil Change?

What Happens if You Don't Get an Oil Change?
LightField Studios/Shutterstock

Going to a mechanic can seem like you’re being taken to the cleaners for services you feel you don’t need. But what happens if you don’t change your oil on time? It can’t be that bad, right?

Actually, it can. Stretching one oil change interval a few hundred miles is probably fine. But regularly ignoring this important maintenance can have dire consequences. Here’s what you need to know if you’re thinking about skipping a service or going well beyond the prescribed oil change interval.

What does oil do in an engine?

Oil is arguably the most important fluid in your vehicle. Oil functions in an engine include:

Preventing wear between moving parts

Oil coats the metal parts inside the crankcase and cylinder head, plus other critical areas such as timing chains. A thin film of engine oil remains on metal surfaces, preventing metal-on-metal wear.

Reducing friction

Oil works to help surfaces easily slip over each other. Increased friction means burning more fuel to create the energy to overcome it. Clean engine oil also improves fuel economy.

Preventing rust and corrosion

Because engines are metal inside, they can corrode and rust when exposed to moisture and air. Clean engine oil prevents rust and corrosion by leaving a film of oil on parts to resist exposure.

Cleaning internal parts

Oil detergents and other additives clean the engine’s internal parts. Minor sludge deposits can be washed away, and debris is suspended in the oil until it can be separated by the filter.

Creating seals

Engine oil also creates a seal between imperfect parts, such as piston rings and cylinder walls. The microscopic oil layer not only prevents the piston ring from chewing into the cylinder wall, it also establishes a barrier so compression doesn’t blow through.

Engine cooling

Oil helps keep the engine cool. It’s responsible for around 40% of your engine’s cooling capacity. It absorbs heat from the denser metal parts and carries that heat to an engine oil cooler, where it’s whisked away

What happens if you don’t change your oil?

If you wait long enough, not changing your oil could result in total engine failure. But if you’re not near a service station or dealership the exact moment your maintenance reminder pings you, don’t panic.

First, oil change reminders estimate when your oil needs to be changed. They are not a warning that your engine will blow up if not maintained precisely on time.

The concern isn’t stretching your car an extra 500 or 1,000 miles before getting an oil change. It’s what happens when you continue to neglect oil changes. Leaving your engine oil and filter changes well beyond the prescribed interval every time has a compounding effect. Neglecting it might not yield results for thousands of miles. But once the oil is so dirty that it clogs oil galleries and bypasses the oil filter, you’re going to see the following consequences come on fast.

Detergent/additive breakdown

Your engine’s base oil is blended with a bunch of detergents, anti-foaming agents, corrosion inhibitors and friction modifiers. These make up somewhere between 15% and 30% of the engine oil. They’re meant to make oil last longer because engine oil naturally breaks down.

Breakdown happens if you don’t change the oil. While there may not be any immediately noticeable symptoms, the neglect leads to the snowballing of the following problems.

Sludge buildup

When detergents in the oil break down, the debris that would normally be captured within oil and trapped in the filter settle in the engine. They attach to metal surfaces and stick in crevices, collecting to form sticky sludge.

Oil starvation happens when you don’t change your oil anywhere close to the recommended interval, and it’s because of sludge buildup. Changing the oil can help bust up these deposits to a certain degree but not always enough to completely reverse the effects.

Component wear

If the engine oil’s protective qualities break down and anti-wear additives lose their effectiveness, the protective barrier on the metal parts is compromised. Like worn-out brake pads, if the barrier is gone, metal parts grind against each other rather than slipping past.

Wear on metal parts can happen to cylinder walls and piston rings, crankshaft journals and bearings, valve lifters and almost any other internal moving part. That’s when long-term engine reliability may be compromised.

Overheating

Heat kills engines. If oil is dirty and low in the crankcase, it’s less capable of absorbing and cooling off heat from the metal parts. That’s compounded by increased friction, so the engine generates more heat than normal. Overheating because of lubrication issues can also seize an engine, too.

Poor performance

Diminished engine performance can occur when there’s more friction in the engine than there should be. Rather than all the parts moving smoothly past each other, revving the engine takes longer and produces less power.

Decreased fuel economy

Dirty engine oil well past its prime affects fuel economy. Friction once again is the culprit, because more energy goes into overcoming the resistance inside the engine. Simply changing the engine oil can help the engine resume normal fuel consumption practices.

Increased emissions

Bad things happen when you don’t change the engine oil, and higher emissions can be a long-term consequence. Excessive heat causes increased levels of nitrous oxide in the combustion process, making for around one-fourth of air pollution. Excessive amounts of oil are also burned because of wear inside the engine. That’s when you see puffs of blue smoke from the tailpipe.

Not changing the engine oil regularly can result in failed emissions tests.

Engine failure

As a worst-case scenario, neglecting to change the engine oil can clog up oil galleries, restrict oil flow, reduce oil pressure and starve your internal engine parts of oil. If all of the symptoms come together, you may have to replace the engine.

An engine failure could be from oil consumption when cylinder walls or piston rings are worn out, or it could be because of seized bearings, overheating or sludge you can’t remove without a rebuild or replacement.

Voided warranty

To add insult to injury, neglecting routine maintenance to your engine could void the manufacturer’s warranty. Although you’d still have warranty on non-engine components, you’d be stuck with the repair bill to fix the backed-up power plant. It’s not the manufacturer’s fault you didn’t follow the clearly defined maintenance instructions.

Conclusion

Not getting oil changes at timely intervals can lead to a costly headache. Oil changes are relatively inexpensive and it’s a service that maintains your car’s reliability and promotes the best fuel economy, especially if you intentionally reduce friction with high-grade synthetic oils. Failing to change the oil can ultimately cost you thousands of dollars, and that’s a hit you shouldn’t have to take while your car’s powertrain warranty is still in effect.


About Bumper

At Bumper, we are on a mission to bring vehicle history reports and ownership up to speed with modern times. A vehicle is one of the most expensive purchases you'll likely make, and you deserve to have access to the same tools and information the pros use to make the right decisions.

Disclaimer: The above is solely intended for informational purposes and in no way constitutes legal advice or specific recommendations.