Why do I need an oil change?

December 23, 2016

When I asked this question to someone who knew a lot about cars, the answer I got was “Oil changes are vital to making your car run smoothly.” I’d heard that before. And sure, I knew that any machine with many metal parts would need to stay lubricated to avoid overheating or something, but since the oil doesn’t really go anywhere, why should I ever need to replace it?

Since car oil lubricates the engine, it seems like it shouldn’t go anywhere unless there’s something wrong with your vehicle. Why is an oil change a scheduled service performed at regular intervals, then? Well, when I Googled the answer, as usual, I found even more I didn’t know about car engines.

As your car runs, it creates an immense amount of heat. That much is obvious from the cloud of hot steam that erupts from your car on a cold morning. This heat is dispersed throughout the engine, greatly affecting your car’s ability to run smoothly. Without oil, the pieces would rub together, creating intense friction, and thus even more heat.

While the oil prevents dangerous heat buildup and fatal engine damage, the heat also takes its toll on your oil. In simple terms, the oil particles start to break down when exposed to the extreme engine heat. This breaking down makes it less effective against the heat it’ll be exposed to in your engine.

(Sometimes, your engine can begin to burn through the oil. For this reason, you should check your oil at intervals, just to make sure your car will still be able to run smoothly.)

The Car Talk site had a pretty good explanation of the service and why it’s necessary. It said, “Oil undergoes thermal breakdown due to high operating temperature. When this occurs, the oil becomes less effective as a lubricant. And, without a good lubricant, parts of the engine rub together and wear each other out. Oil also contains additives that have the ability to neutralize acids. Over time, these additives get used up and stop being effective. Finally, oil can absorb water, dust and combustion byproducts and also hold them in suspension. Eventually, the oil gets saturated with this stuff and can't absorb any more. Then that stuff remains in the engine and can cause corrosion.”


Replacing old oil will prevent the parts in your car from being damaged by your car’s heat, and even the natural wearing down of your engine that’s caused by the foreign particles in your car. The only catch is that there are plenty of different kinds of oil that protect your car to different degrees, and for different lengths of time.

Each car is assigned an oil weight by its manufacturer. The weight of the oil describes its viscosity, or thickness, and how it reacts to different temperatures. Much to my relief, that’s something I don’t have to worry about. It’s decided by my car’s manufacturer, so it’s the least of my concerns. 

But, when you get an oil change, you’ll usually be offered a few different kinds of oil within your oil weight category: a conventional option, a synthetic, and a blend of the two. Conventional oil is the classic oil option that’s purified to give you reliable protection from engine heat and engine friction. This option is usually the cheapest, and works well in keeping your engine running smoothly. The synthetic and conventional blend option is mostly targeted at cars with high mileage, but works really well if it’s used with any vehicle. It works to to keep your engine clean, and helps to slow the usual wear and tear your engine can suffer over the years. This option, understandably, is priced between the synthetic and conventional options. The synthetic option is designed in a laboratory to create the least buildup in the engine, and to defy the oil breakdown that occurs at high temperatures. This oil usually lasts a few thousand miles more than the conventional, and is designed to keep cars in good shape for as long as possible. This option, because of its how it’s made, costs more than the other two options, but will last significantly longer. While some vehicle manufacturers strongly recommend either the high-mileage blend or the synthetic option because of your engine type, this choice is otherwise up to you. 

Engine oil is really important to your car’s ability to run for a long time, and it’s especially important to it’s ability to run smoothly. For this reason, you should check your engine oil regularly, and be sure to come in as soon as your car requires more oil. (Usually, the company that changed your oil last will put a sticker on the drivers’ side of your windshield that shows the mileage for your car’s next oil change.) While it may seem like a somewhat useless service, oil changes keep your car in shape. Keeping up with your oil changes will keep your engine cool enough to run smoothly. It will also keep your engine going for much longer.