5 Things to Know About Oil Changes for Your Car

Understand when and how often to change it, what type your car needs, and more

Even as cars become increasingly sophisticated, motor oil remains the engine’s lifeblood, and caring for this fluid is vital. Fortunately, this is a rather simple task—and your car’s onboard computer can help.

Many cars have a built-in service minder that signals when an oil change is needed, based on usage, and some will even indicate if the oil level is low. But it is still smart to check the fluid yourself every other fill-up. It may seem redundant, but it is a good excuse to inspect underhood, checking other fluid levels and looking for anything else that may cause trouble, such as a worn belt, loose parts, or signs of animal nesting.

Below, we provide answers to five common oil-related questions, with expert insights from Consumer Reports’ resident car mechanics John Ibbotson and Mike Crossen.

Motor oil needs to be changed when it is either worn or aged out. The oil degrades from heat and pressure, and it can collect harmful particles that need to be removed. Plus, oil breaks down over time, even when the car is parked for an extended period.

Fortunately, the specific guidance for your car can be found right in the glove box. The answer to this question, and many others, is to check your owner’s manual. It should be your car maintenance and operation bible. Don’t make assumptions on the interval based on past experiences or guidance from mechanics who profit from the work, because the timing has evolved over the years.

The built-in service reminders are a great convenience. “These systems typically monitor the number of miles a vehicle has traveled, and they also track how hard the car is being driven, and adjust accordingly,” Ibbotson says. Think of it as an onboard personal adviser.

When buying a new or used car, be sure to read the manual to see if it is equipped with a reminder and how it works. Some minders have settings, including the ability to turn them off. If you buy a used car, take the time to confirm that it is set up as expected. You don’t want to either keep waiting and waiting for a light to signal an oil change that will never come, or misinterpret a light that is meant to indicate a tire rotation, rather than an oil change.

Our mechanics recommend checking your oil level at least once a month, or ideally every other gas fill-up. Don’t assume that a new car is exempt from this maintenance chore. Consumer Reports reliability survey results have shown that even newer cars can need the oil to be topped off between changes.

Check the owner’s manual and follow the automaker’s recommendations. Some newer cars have electronic oil monitors and don’t have traditional dipsticks for manual inspection.

Photo: iStock Photo: iStock

If you do have a dipstick, and you’re checking it yourself, make sure the car is parked on level ground. If the engine has been running, be aware of potential hot spots under the hood. Most automakers recommend checking the oil level when the engine is cool.

With the engine off, open the car’s hood and find the dipstick. Pull the dipstick out from the engine and wipe off any oil from its end with a dust-free cloth or towel. Then insert the dipstick back into its tube and push it all the way back in.

Pull it back out, and this time quickly look at both sides of the dipstick to see where the oil is on the end. Every dipstick has some way of indicating the proper oil level, whether it be two pinholes, the letters L and H (low and high), the words MIN and MAX, or simply an area of crosshatching. If the top of the oil “streak” is between the two marks or within the crosshatched area, the level is fine.

If the oil is below the minimum mark, you need to add oil. (Use the oil type recommended in the owner’s manual, adding just no more than half a quart at a time. Let the car sit, then check again.)

Pay close attention to the old oil’s color. It should appear brown or black. But if it has a light, milky appearance, this could mean coolant is leaking into the engine. Look closely for any metal particles, too, because this could mean there is internal engine damage. If you see either of these conditions, get the car to a mechanic for further diagnosis.

If everything is okay, wipe off the dipstick again and insert it back into its tube, making sure it’s fully seated. Close the hood and you’re done.

If the oil is consistently low when checked, the engine is either burning the oil or leaking it. Either way, discuss this recurring issue with your mechanic.

The “every 3,000 miles or every three months” rule is outdated because of advances in both engines and oil. Many automakers have oil-change intervals at 7,500 or even 10,000 miles and six or 12 months for time.

“Your owner’s manual has more detailed information about your car than any mechanic does,” Ibbotson says. “Don’t get talked into too-often oil changes. Follow the manual and your car’s engine should stay well-lubricated and perform well.”

Photo: Getty Images Photo: Getty Images

Over the course of two years and 30,000 miles, assuming that your oil change costs $60 a pop, you could save $360 if you get it changed every 7,500 miles vs. every 3,000 miles.

It’s not just about miles: If you don’t drive your car a lot, your oil still needs to be kept fresh. Even if you drive fewer miles each year than your automaker suggests for changing the oil (say, 6,000 miles, with suggested oil-change intervals at 7,500 miles), you should still be getting that oil changed twice a year.

Why? Oil becomes less effective as it ages, and by not getting the engine warm enough, excess moisture that forms in the engine will not be removed, which can lead to shorter engine life.

Visit our guide to car maintenance and repair.

Again, take a look at your owner’s manual. “Don’t be upsold into synthetic oil if there is no need,” Ibbotson says.

In many newer models, the weight of your car’s motor oil is printed on the cap where you add oil, and it is definitely listed in the maintenance section at the back of the owner’s manual. “Make sure you know what’s recommended or required by your automaker before you visit your mechanic so that you can control the cost of the oil they’re putting in,” he says.

Photo: John Powers/Consumer Reports Photo: John Powers/Consumer Reports

If you have a much older car, do you need special motor oil?

“Not if it’s running well,” Ibbotson says. “If you’re not sure what oil you should be using because you don’t have an owner’s manual, check with your local dealer or an online enthusiast group for your particular model,” he says.

Don’t get creative with your engine oil choice. The automaker spent many millions of dollars to develop the engine, and it chose the recommended oil for a reason.

When changing the oil, be sure to use an original equipment or premium-grade oil filter, rather than a budget filter.

Not necessarily. For most drivers, it isn’t worth upgrading from conventional oil to synthetic.

“Only if your manufacturer calls for it,” Ibbotson says, “because it can cost from two to four times as much as conventional oil.”

Synthetic oil is designed to be more effective at resisting breakdown (and because of that, it lasts longer) and withstanding high temperatures.

Photo: Getty Images Photo: Getty Images

But he advises that there are situations where that resistance to breakdown can help prolong the life of your engine, making the upgrade worthwhile.

“If you make lots of short trips, standard motor oil may never get warm enough to burn off moisture and impurities, which means it may not be doing enough to protect your engine,” Ibbotson says.

Another consideration is your lifestyle. “If you live in a region with very cold winters or very hot summers, or if you use your vehicle for towing or hauling heavy material, synthetic oil is your best bet,” he says. “While synthetic generally holds up better and can serve for more miles, it is equally important to not extend oil changes beyond the time interval recommended by the manufacturer—typically six months or a year if it is a motor that is not driven many miles or on many short trips.”

Synthetic oil can also help engines that are prone to building up sludge; some Volkswagen and Toyota models had sludge issues in the past. This residue, formed when oil breaks down, can block the flow of oil, leading to the quick death of an engine. Synthetic oil would be beneficial in these engines because it helps to reduce sludge buildup, helping to extend the engine’s life span.

There are a lot of misconceptions when it comes to keeping your car running smoothly. On the “Consumer 101” TV show, host Jack Rico learns from Consumer Reports’ expert Jon Linkov the truth behind some of the biggest maintenance myths.

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