Just like the human body needs water, the engine in your car needs oil (unless it’s a pure electric vehicle, in which case it doesn’t have an engine). That said, there are all sorts of different oils, and, adding to the potential confusion, the type of oil required can vary from vehicle to vehicle. Keep reading to learn the basics, including what types of engine oils are available and the importance of checking and replacing your oil regularly.
Your Car Needs Oil
Simply put, oil is the lifeblood of your vehicle. Inside your engine are hundreds of precision-crafted metal parts working in unison under extreme temperatures and stress. Oil, which relies on pressure to move throughout your engine, keeps all those bits and pieces lubricated and moving efficiently. Without the correct amount and type of oil, the friction between the engine’s internal components can eventually lead to catastrophic failure. That’s not good. Running your car with dirty oil (full of contaminants, often due to infrequent oil changes) is equally problematic, as it fails to lubricate as well as new oil. Clean oil will typically have an amber color, while used or dirty oil will appear black.
If the oil-pressure light on your dashboard lights up, that’s an indication that your oil level is low and you need to stop the engine immediately to prevent possible damage. Along that same vein, if you know your engine burns oil or you’ve seen evidence of an active oil leak, be sure to check the oil level frequently and keep an extra quart or two in your car to top off as necessary. Indications of oil loss or excessive consumption include drops or puddles of fluid on the ground below the engine, a wet appearance on parts of the engine suggesting oil is getting past failed gaskets, a burning smell while driving caused by oil or another fluid leaking onto the exhaust, or blue smoke coming from the tailpipe (meaning oil is being burned due to an internal engine issue).
Make Sure You're Using the Right Oil
Keeping track of your oil level is simple. However, choosing the correct oil for your engine can be more challenging. There are two general types. The first is what we’ll call conventional motor oil, which is a refined version of the crude or natural gas pumped from the ground. It’s the same stuff your parents likely used, their parents used, and so on, though it has been enhanced over the years with various additives to provide better engine protection. When you go into your local quick-lube service station and ask for the cheapest oil change available, this is the oil you’ll get.
The second type of oil is synthetic, which, as its name implies, consists of man-made chemicals or crude that has been chemically altered. Like conventional oil, synthetic oil contains additives that protect the engine by, among other things, preventing corrosion and the buildup of harmful sludge. Synthetic blends, using both conventional and synthetic oil, are also available.
Each of these types has advantages and disadvantages. Conventional oils are cheaper to produce, but they break down (or become contaminated) more quickly. Synthetic oils are engineered to last longer, meaning they don’t degrade like the conventional type and, therefore, provide an extended service life. For example, a typical conventional oil change may cost roughly $25-40 and last 3,000 miles, whereas using synthetic oil may increase the price to $70-100 but potentially push the service interval to upwards of 12,000 miles.
Synthetic oils also have an advantage when it comes to operating temperatures, which is reflected in ratings like 5W-30 or 15W-40, where the numbers represent viscosity at different temperatures (and W stands for winter). The lower the number, the lower the viscosity. So 5W-30 oil, for example, has a low viscosity (5) at cold temperatures and, therefore, flows more freely, while at higher temperatures the oil becomes more viscous (30) to prevent thermal breakdown and possible engine damage. Both synthetic and conventional oils are designed to handle these extremes, but synthetics do so more efficiently.
One thing many of these oils have in common is an API certification symbol on their packaging. That refers to the American Petroleum Institute, which tests and verifies that these products meet international standards. You’ll also see the API service symbol detailing the oil’s performance level (with differing designations for gasoline-engine and diesel-engine oils), its viscosity, and more. Consult your owner’s manual or your local dealership’s service department to determine which oil is best for your vehicle.
Know When to Check and Replace Your Oil
To determine when your oil should be replaced, you’ll first want to consult your owner’s manual. Typically listed under maintenance, you’ll see recommended intervals based on time and mileage (such as one year or 12,000 miles), as well as driving conditions (normal and severe). Depending on which oil you use and how and where you drive, your vehicle may require oil changes anywhere from every 3,000 to every 12,000 miles.
Perhaps more important than staying on top of oil changes is remembering to check your oil. It’s a good habit to check the dipstick whenever you stop to fill up for fuel. When parked on level ground, simply open the hood, look for the brightly colored pull tab marked Oil, and pull it out. At the bottom of the dipstick will be markers that indicate the oil level—if it's low, add oil (but be careful not to overfill). If it’s dirty, schedule an oil change, or do it yourself with only a few basic tools (and remember to put in a new oil filter at the same time). Make sure to replace the oil with the recommended grade and, to save a few dollars, consider purchasing a full case rather than individual quarts. You’ll often find the best deals at big-box stores like Walmart and even Home Depot. Store any unused oil in an area where the temperature remains consistently between 40 and 75 degrees, but discard if the oil has been sitting for more a couple of years (additives can begin to separate and yes, even oil has an expiration date).
For those times when you find yourself down on oil and without an extra quart in the trunk, it is acceptable to top off with whatever’s available at the gas station. However, it’s not advised to make a habit of mixing oils, as properties can vary based primarily on the additives used by different brands.
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Updated on: March 10, 2020