When it comes to routine maintenance, changing your oil is one of the more inexpensive services. Despite its relatively low cost, oil plays an important role in your engine’s performance and longevity, and spending a little money on routine oil changes can help prevent you from forking over large sums of cash down the road.
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. Increasingly now in modern engines, there is a fourth function. Engines with Variable Valve timing use pressurized engine oil to adjust the camshaft timing for optimum performance and mileage.
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 filler 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. Some manufacturers also specify a particular level of performance for oil in their cars, most recently GM with their Dexos specification for vehicles they built in 2011 and later.
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 manufacturers saying up to 15,000 miles is OK.
Where and how you drive can influence how often you need to change your oil. Factors include extreme heat and cold, 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.
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.
Also, 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.
Another problem 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, which can plug up passageways in the variable valve timing actuators or in severe cases, oil pump pickup screens, causing major engine damage.
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.