What Type of Oil Does My Car Need?

With so many options, choosing the right motor oil can be bewildering. We cut through the confusion to help you make the best choice for your vehicle.

What you need to know before changing your oil

Using the wrong oil can result in costly engine damage. With so many options on the market, choosing the right oil for your vehicle can get confusing. Here’s what you need to know before changing your oil.

What Is Motor Oil?

Motor oil is an engine’s lifeblood — a truly amazing substance. It pumps throughout the running engine via small passages called galleries, cleaning, lubricating, cooling and cushioning moving engine parts while holding sludge, abrasive particles and harsh chemical contaminates in suspension. Old motor oil needs to be changed periodically to keep your engine running smoothly.

Read the Labels

Choose an oil with the vehicle manufacture’s recommended viscosity rating (check your owner’s manual). Viscosity is an oil’s ability to flow at different temperatures. The two most common viscosities (a.k.a. weights) are SAE 5W-30 and SAE 10W-30. The lower the number, the thinner the oil.

Beware the “W.” It stands for winter, not weight. Called multi-weight oils, they perform in a wide range of temperatures, reducing surface wear between engine parts. Keep this in mind when oil shopping, especially if the climate where you live has wide temperature fluctuations (0 degrees F in the winter to 100 F in the summer).

Types of Motor Oil

Conventional motor oil begins its life in the ground as crude (base) oil. It is then refined to remove impurities and blended with different chemical additives. Those additives include detergents to neutralize sludge, antioxidants that inhibit metal degradation, and anti-foam agents that prevent air bubbles. This is the least expensive type of motor oil.

High-mileage motor oil is formulated for vehicles with 75,000 miles or more on the odometer. This oil contains additives and chemical enhancers that can cause internal and external O-rings and gaskets to swell, potentially reducing oil leakage and burning in older engines. High-mileage motor oil will not fix mechanical failures or excess wear. But if your vehicle has been properly maintained and is running and performing well, high-mileage engine oil might be the right choice to extend the life of critical engine parts. It might keep your vehicle running much longer than planned.

High-mileage motor oil can be formulated from conventional, synthetic-blend or full-synthetic motor oil and will be priced similar to those types of oil.

Synthetic-blend motor oil is the best of both worlds. It is a mixture of synthetic and conventional base oils with additives found in both. It has excellent engine protection properties at a lower cost than full synthetics. Full-synthetic motor oil is ideal for vehicles that demand ultimate levels of protection. This type of motor oil is in the middle price range.

Full synthetics begin with base oil. However, extensive refining processes remove more impurities than with conventional oil. And the addition of artificially made compounds and higher performing additives help keep an engine cleaner and protect it from damage. Synthetic oil, although superior, is not recommended for all vehicles. Older model vehicles are designed to use conventional oil. Full synthetic is the most expensive type of motor oil.

Can I Mix Different Types of Oil?

Yes, but don’t. It is a waste of money. Even if you add full synthetic to conventional oil, you still end up with only the properties of a conventional oil. Synthetic blends are formulated with different additives to better protect an engine against wear, high heat, cold weather and sludge build-up not found in conventional oils.

When choosing a motor oil, consider the type of driving you do. Harsh driving conditions, such as city vs. highway, off-roading or along dusty, dirty roads, require motor oil to work harder and be changed more frequently. Short trips of less than 15 minutes make up the most severe driving conditions. If the engine doesn’t reach top operating temperature consistently, it can’t burn off water condensation, allowing sludge build-up to form.

Always refer to your owner’s manual to determine which motor oil is recommended to protect your vehicle. Be sure to dispose of used oil properly.

Robert Lacivita
Bob Lacivita is an award-winning auto technician and career and technical educator and freelance writer who has written about DYI car repairs and vehicle maintenance topics, as well as writing state, federal and organizational foundation grants, and helped design a unique curriculum delivery model that integrates rigorous, relevant academic standards seamlessly into technical/vocational training, for more than 20 years. His work has been featured in Family Handyman, a Reader's Digest book and Classic Bike Rider magazine, among others. Bob and his wife lived through 20 years' worth of DIY home remodeling while parenting two (now grown) boys and now relax by watching their three fabulous granddaughters.