Why Oil Matters

When it comes to routine maintenance, changing your oil is one of the more inexpensive services. Despite its relatively low cost, oil plays a vital, multifaceted role in your engine, and spending a little money on routine oil changes can help prevent you from forking over large sums of cash down the road.

The Role of Oil

Engine oil provides three key functions in a modern internal combustion engine. First of all, it helps keep engine components working smoothly together. Secondly, the inside of an engine, a place where there are thousands of controlled detonations happening every minute, can be a hot place, and oil helps draw heat away from the combustion chamber. Lastly, it helps prevent carbon and varnishes from accumulating in the engine.

What Oil Should I Use?

There are many types of engine oil, but it's fairly easy to determine what kind you should use in your car. Your owner's manual should tell you the appropriate viscosity of oil — like 5W-30, for instance — that your engine requires, and the viscosity may also be stamped on the oil reservoir cap on the engine itself. Viscosity is the measure of how much resistance a fluid has to flowing. Many would refer to it as the "thickness" of a fluid; honey has more viscosity than water, for example.

There's more to oil, though, than just viscosity. The American Petroleum Institute certifies oil based on performance criteria determined by automakers, engine builders and oil producers. Oils that meet the standards receive the API Certification Mark, which should be easy to see on an oil container.

How Often Should I Change My Oil?

Oil changes are often recommended when a certain mileage or time limit is reached. The most familiar interval is 3,000 miles or three months, but what's more important — the mileage or the time?

Experts say trust the odometer, not the calendar. Driving has far more of an impact on your engine oil; if a car is sitting, there is less need to replace the engine oil. Oil-change intervals used to be much more frequent than they are today. Around 50 years ago, you would have had to change your oil every 500 miles. Today, the drain intervals for some oils dwarf even the 3,000-mile standard, with some special performance oils recommending changes at 15,000 up to 35,000 miles.

Where and how you drive can influence how often you need to change your oil. Factors include extreme heat, towing a trailer and driving where there's dust and sand.

What if I Don't Change My Oil?

In short, it's not pretty.

One of the problems is that there will begin to be buildup in the cooler parts of the engine, like the crankcase and around the camshafts and valves. This can lead to carbon deposits, or sludge, coming out of the old oil. That could require an expensive engine cleaning or force you to replace worn-out piston rings.

It can get worse. The pistons could eventually seize or the camshafts could be damaged. Getting a bill for either one of these repairs would make even a few high-quality oil changes look like pocket change. Consider regular oil changes to be like really cheap insurance for your engine. 

© Cars.com 05/31/2013