Choosing the Right Motor Oil for Your Car
If you've read the other pages on this site looking for some information that would make it easier to choose a motor oil, you're probably disappointed. Motor oil is much more complex than most people realize. The more you know about oil, the harder it is to choose one.
We oil geeks do love to agonize over even the most minute aspects of oil. If that's what you want to do, I recommend that you visit Bob is the Oil Guy. No characteristic of oil is too obscure to discuss in great depth on BITOG.
If what you're looking for is some general advice about choosing a decent oil (and avoiding the really bad oils), then this page is for you. I'm going to try to keep it simple here.
Before I go on, if the car you're buying oil for has a GDI (gasoline direct injection) engine or T/GDI (turbocharged gasoline direct injection) engine, please read this page first. GDI and T/GDI engines have special considerations that affect oil choices. Otherwise, let's take a look at the steps involved in choosing a motor oil.
Check the Vehicle's Owner's Manual
This is the first step in choosing an engine oil for any vehicle or machine. The owner's manual will, at a minimum, specify the viscosity or viscosity range, and the service rating, for oil for your vehicle's engine. For example, a recent model year car may allow for the use of 5W-20, 5W-30, or 10W-30 oils (viscosity) and a service rating of (SN North America), A5/B5 (in Europe), or GF-5 (ILSAC). At a minimum, the oil you choose must meet these standards or a more recent superseding standard (for example, SP supersedes SN Plus and all previous "S" ratings, and GF-6 supersedes GF-5).
In some cases, the manufacturer may also specify a manufacturer-specific approval, such as General Motors' Dexos® standard. You must limit your oil choices to oils meeting any such requirements. Failure to do so could affect your vehicle's warranty, no matter how good the oil is otherwise.
Be aware, however, that manufacturer requirements are minimum standards. You can always use a better oil as long as the governing board (for example, API in North America) recognizes that oil as meeting the requirements of the specified oil. For example, if you live in North America and have an older car whose owner's manual specified API SM oil, you can use SN or SP oil because API has stated that the most recent "S" standard supersedes and incorporates all previous "S" standards; so an SP oil meets or exceeds the requirements for SM, SN, and SN Plus. (Note that this is not how European ACEA ratings work. ACEA ratings are not necessarily sequential.)
Finally, be aware that the service ratings themselves are minimum standards that oils must meet to bear the governing authority's seal. There are oils that barely meet those requirements, and there are oils that far exceed them. The cost of quality oil is trivial in the big picture of car ownership. I advise you to aim high when it comes to motor oil.
Decide Between Synthetic, Conventional, or a Blend
If you haven't already read the page about base oils, doing so now may make this section easier to understand.
Synthetic motor oil is the oil of choice for all or nearly-all new or newish cars. Its superior lubricity, viscosity stability, extreme-temperature performance, detergency, and volatility qualities make it the common-sense choice for most modern vehicles. Some of my favorite synthetic motor oils include Castrol Edge Titanium, Pennzoil Ultra Platinum, Valvoline Modern Engine Oil, Mobil 1, and Amazon Basics Synthetic.
There are some cases, however, when you may want to consider a high-quality conventional oil or a conventional / synthetic blend. For example, you may want to choose conventional motor oil or a blend if:
- Your vehicle's manufacturer or your dealership recommends against synthetic. This is highly unusual.
- Your vehicle's engine was just overhauled or has had major internal work done. Synthetic oils aren't as good at carrying metals in suspension as conventional oils are. Many mechanics recommend using a conventional oil or a blend for the first oil fill after an engine has been overhauled or has had internal work done on it.
- You drive an older vehicle that has always used conventional oil. Once in a while, switching to synthetic oil in an older vehicle can wash away sludge that is effectively acting as engine seals. This dislodged sludge can also clog the oil filter. If you do switch to synthetic in an older car, I advise that you keep the first oil and filter change interval short. I usually keep the first change interval to about 1,000 miles (about 1,600 kilometers) when switching from conventional to synthetic motor oil in an older car.
- Your vehicle has more than 75,000 miles (about 120,700 kilometers) and is showing signs of age such as oil leaks or lost compression. In that case, you'll want to consider a high-mileage motor oil. Both conventional and synthetic high-mileage oils are available. My favorite high-mileage oils are Castrol Edge High-Mileage, Valvoline Synthetic Blend High-Mileage, AmazonBasics High-Mileage, and Pennzoil High-Mileage.
- You drive an antique vehicle with special oil requirements.
If I were recommending a conventional motor oil for a family member or friend, Castrol GTX, Valvoline Daily Protection, Pennzoil, and AmazonBasics Conventional would be high on my list of recommendations.
Be Careful With Generics and Store Brands
Note that I didn't say, "Never use them." Some store-branded oils, like AmazonBasics, are very good. But some aren't. So do your due diligence and research a generic or store-brand oil before buying it. BITOG would be a good place to start researching.
Don't Just Choose the Cheapest Oil
With motor oil, as with most things, you get what you pay for. High-quality oils are exquisitely engineered and painstakingly manufactured to provide the best-possible performance, and all that care and attention to detail costs money. As a percentage of the total cost of owning a car, the few dollars (or pounds, or pesos) that you save by buying an inferior oil just aren't worth what you're giving up.
I do understand, however, that there are folks for whom every dollar (or pound, or peso) may mean the difference between eating and going hungry for a day or two. If you're in that situation, consider AmazonBasics motor oil. It's a good oil and a good value.
Choose a High-Quality Oil Filter
The longer oil-change intervals that modern engines and synthetic motor oils have made possible make it especially important that the oil filter be changed along with the oil.
Choosing a quality oil filter is even more important than choosing a good oil. Unlike oil, which has to meet certain specifications to bear the governing bodies' seals, there are few standards regulating oil filters. Consequently, there are some truly horrid oil filters on the market.
Cheap oil filters usually have cheap paper media that is prone to tearing and deterioration; inferior bypass valves that can cause oil starvation if the filter gets clogged; and faulty anti-drainback valves that can cause oil starvation when starting the engines of some cars. Cheap oil filters should be avoided like the plague.
My preference is to use oil filters made by the car manufacturer whenever possible. They're usually very good filters, they avoid any potential warranty issues, and they're usually (but not always) reasonably priced. So when choosing an oil filter, include the car manufacturer's filters in your possible choices. They may be more affordable than you think.
When the manufacturer no longer sells filters for a particular car, when they're ridiculously expensive, or when the nearest dealership is just too far away, WIX oil filters are always my go-to choice. They're famous for their consistent quality, compatibility, and attention to detail. Even though I usually use OEM filters whenever possible, I wouldn't hesitate to use a WIX oil filter in any car I own.