Motor oil lubricates engine parts, eliminating friction between them. Over time, however, oil burns off—or leaks out—of the engine, requiring replacement. Knowing which motor oil is right for your car ensures your engine performs efficiently.
We recommend checking your oil at least once a month when you stop to fuel up. If you know your car is prone to leaking oil or burns through oil quickly, check it every time you fill the tank to learn its rhythm and keep it above the half-full line on the dipstick.
As most wise mechanics will tell you, “any motor oil is better than no motor oil” when your engine is in need. That said, motor oils come in various formulations, each with its own niche attribute.
The owner’s manual is always the best place to learn which oil is best for your vehicle’s make and model. If you purchased a used car and it doesn’t have a manual, search for one online.
Use CarFax’s Links to find your car’s manual based on model and year.
Motor oil is made and labeled based on several different features.
Viscosity describes how a liquid moves based on density and flow. In this case, the more viscosity a fluid has, the thicker and slower it flows. So, for example, maple syrup is more viscous than water, but honey is more viscous than warm maple syrup.
The more viscous the motor oil, the longer it takes to move through the engine—especially when the weather is cold. That’s why your owner’s manual may recommend one engine oil for warm weather but a lighter weight oil for colder weather—especially if you live or drive in areas with freezing temperatures.
Historically, motor oil was all made from crude oil. However, that’s no longer the case. Today, average street motorists have a choice between three different types of oil:
Fully synthetic oils are chemically modified crude oil. Most new cars - (except for electric cars that don’t use oil at all) are rolled out of the factory with synthetic oil and run more efficiently as a result. Synthetic motor oil has exceptional heat and oxidation resistance, lasting longer than standard motor oil. Another benefit of synthetic oil is that it functions well regardless of temperature extremes.
The cars of the 80s and 90s needed oil changes every 3000 miles, whereas cars using synthetic motor oil only require oil changes every 10,000 miles or so (but you should consistently check oil levels to ensure you’re not running low). So, while the oil is more expensive at the outset, it lasts longer and these costs average out over time. Increased fuel economy is another cost-saving benefit of using synthetic oil.
Conventional oil has decent resistance to heat and oxidation, but it burns off more quickly. As a result, cars using mineral oil should pull into the oil changing station every 3,000 miles or so. This may make you want to switch to synthetic, but most mechanics recommend sticking with mineral oil if that’s what your car engine is used to. If you want to make the change, schedule an appointment with your mechanic to see what they recommend.
Conventional motor oil is more likely to contain impurities that eventually gunk up the engine, although regular service appointments to perform recommended maintenance take care of this. Also, your engine may want something else if you live in—or will be traveling in—extreme temperatures.
As you can imagine, semi-synthetic oil combines synthetic and mineral oils to meet halfway with the benefits. Semi-synthetic motor oil is less expensive than synthetic oil but lasts longer than mineral oil. Usually, vehicles using semi-synthetic oils require changes every 5000 miles.
This is a good fit if you want to upgrade from synthetic oil options but don’t want to pay the extra money for pure synthetic oil. Also, unless you’re in true extreme temperatures, you don’t need to change your oil type for different seasons.
If you’re driving a car with 75,000 miles or more, it needs extra TLC. Motor oil manufacturers have you covered with specialty blends of high-mileage oil. These oils contain additives that help prevent oil from leading and burning, increasing oil efficiency. It can also help to reduce an older car’s emissions.
You’ll also notice that motor oil bottles have labels that read SAE 5W-30, 15W-40, or 10W. What’s that all about?
This stands for the Society of Automobile Engineers. So, the label tells you that the oil inside falls under one of the multiple standards set (and tested) by the SAE.
Since motor oil viscosity affects engine performance, especially in winter temperatures when oil is notoriously sluggish, manufacturers indicate what the oil weight is in average winter temperatures. Therefore, the letter “W” indicates the oil’s viscosity rating in cold weather.
The higher the number, the greater the viscosity. And remember, the higher the viscosity, the thicker the oil and the slower it moves. So, low numbers represent thinner oil and higher numbers represent thicker oil. So, an oil labeled SAE 5W-30 indicates that the oil has a viscosity of 5 during the winter but as efficiently as a 30 in warmer temperatures.
If you don’t want to worry about what oil to use when most manufacturers recommend using a 5W-30 as it works optimally in a range of temperatures. If you’re on a summer road trip across the southwest, where temperatures will be very warm to hot, you may want to change to a higher-weight oil - like a 5W-40.
On the other hand, if you head up into the mountains regularly during ski season, talk to your mechanic or your favorite oil changing station about whether you should replace your oil with a 5W-20.
Failing to check your engine is a major no-no. It leads to overheating and complete engine breakdown, which could mean needing a whole new engine to get back on the road again. If you find yourself on the side of the road with a smoking or malfunctioning engine, the J & T Towing crew is here for you. Contact us ASAP, or call 707-366-4189, and we’ll have a friendly roadside assistant out to you as soon as we can.
