You hear the pitch constantly from lube shops and quick-oil-change places: You need to change your oil every 3,000 miles. You want to keep your car running as smoothly as possible, so you listen, dutifully driving your auto to the nearest oil-change shop every time your odometer cracks the 3,000-mile mark. But you can’t help but wonder why changing your oil is important. What, exactly, does oil do for your car?

The key fact to understand about oil is that it is a lubricant. Run it between your fingers. You’ll see that it’s extremely slippery. This is important for your car’s engine. Remember, car engines are pretty violent places. Small explosions, flashing pieces of metal and plenty of moving parts all combine to propel your car down your city’s streets.

Without oil, these moving parts would constantly be rubbing against one another hard enough to create fission. And fission is one thing you don’t want in a car engine. It heats your engine to unsustainable levels. If you skip the oil change for a long enough period of time, smoke will belch from your vehicle’s front hood as you drive down the street. You’ll also severely damage your car’s engine. That’s an expensive repair.

An oil change accomplishes two things: First, it will ensure that there is enough oil in your car to keep your engine fully lubricated. Secondly, it will replace dirty, old oil with fresh and clean oil.

Dirty oil forms clumps that get caught in your engine. You may hear mechanics refer to these clumps as gunk. Gunk gets hot when your engine is firing. When its stuck to the sides and tops of your engine, this hot gunk can increase the heat of your entire engine, leading, again, to serious problems.

If you haven’t had your regular oil change, then, make sure to stop by your local lube shop. Yes, it will cost you money – anywhere from $15 to $60 or so, depending on your lube place – and it will take time out of your day. But isn’t the relatively small charge of an oil change, plus the 15 minutes or so it costs you, fair prices to pay to make sure that your car is running as smoothly as possible?

Don’t ignore the call of an oil change. Now that you know why an oil change is so important for your car, you have no excuse for skipping your regularly scheduled one.