Should You Use Conventional or Synthetic Engine Oil?
Estimated reading time 9:00
Are there advantages to using synthetic oil vs. conventional oil in your vehicle? We all know that it’s critical to change your motor oil on a regular basis. Doing so removes contaminants that have built up. Regular oil changes help your engine perform better and last longer.
There are many brands of motor oil on the market. When it comes to synthetic vs. conventional oil, there are many types. This list includes full synthetic, synthetic blend, and conventional. Some people refer to conventional oil as regular oil.
They make oil for many applications, including passenger cars and high-performance vehicles. Also, they make special engine oils for race cars. Several factors determine whether you should use synthetic vs. conventional oil.
So, what’s the difference between synthetic and conventional oil? Let’s first discuss the role oil plays in your vehicle.
What Does Oil Do In A Car?
Regardless of whether it’s synthetic oil vs. conventional oil, one thing is true. Motor oil has a very complex job. It provides vital lubrication and separates moving metal parts in the engine. These parts move at high speeds and will wear down if not lubricated.
A vehicle engine operates at low temperatures. But, it can operate at very high temperatures, sometimes extreme. Besides lubrication, engine oil has many other important functions:
- Reduces engine wear
- Keeps engine parts cool
- Prevents deposits from forming on internal engine parts
- Suspends and remove contaminants in the oil
- Protects the engine across a wide range of temperatures
- Provides optimal fuel efficiency
- Conditions seals
When comparing synthetic vs conventional oil, they have four primary functions.
Those functions are lubricate, protect, cool, and clean.
Difference Between Synthetic Oil vs Conventional
All motor oil pretty much looks the same. You might wonder, “What’s the difference between synthetic oil vs. conventional oil?” The fact is there are notable differences between synthetic vs conventional oil:
- How they’re refined
- The additives they use
- Their performance.
So, which is the better when it comes to synthetic vs. conventional oil? Let’s examine to help you understand what makes them different.
What Is Conventional Oil?
Conventional oil is a mineral-based oil that comes out of the ground (crude oil). They process it through a refinery. Base oils fall into one of several oil grades, ranging from Group I to Group V.
They classify conventional base oils as Group I or Group II oils. Group I is solvent-refined while they refine Group II oils by hydrocracking. Hydrocracking adds hydrogen under high pressure with a catalyst. The process breaks the hydrocarbon molecules into simpler molecules.
Both Group I and Group II base oils have a lower viscosity index than Group III, IV, or V.
What Is Synthetic Oil? What Is Synthetic Oil Made From?
They invented synthetic oil in the late 1920s. The term “synthetic” doesn’t mean that it’s derived from man-made ingredients, as the name implies. “Synthetic” is a marketing term. They make synthetic oil from natural ingredients, usually crude oil. They also use high-quality base oils treated with chemicals.
The process cleans up the molecules. It makes them almost the same size, shape, and structure. They also include additives that enhance the oil’s performance. Synthetic oil falls into the Group III, IV, and V base oil categories.
A Group III synthetic oil is more refined through hydrocracking than a Group II base oil. The refining process is also longer, resulting in a purer base stock.
A Group IV base stock is a polyalphaolephin (PAO). This is the most common synthetic base oil for industrial and automotive lubricants.
Group V base oils are polyalkylene glycols (PAGs) and various esters. They rarely blend a complete Group V product. Instead, it’s used as an additive to enhance the performance of a Group III or IV base oil.
Group III, IV, and V base oils all have a higher viscosity index than Groups I and II. This means the viscosity changes less during startup and operation as the temperature changes. The oil is more stable. Plus, these base oil groups resist oxidation, thermal breakdown, and oil sludge. They may also improve horsepower and torque.
Now that you have a better understanding of conventional vs. synthetic oil, let’s discuss full synthetic oil vs synthetic blend.
Synthetic Oil vs Synthetic Blend
There is a difference between full synthetic oil vs. synthetic blend. What is synthetic blend oil? It’s a combination of mineral (conventional) and synthetic base oils. Synthetic blend oil provides added resistance to oxidation and has outstanding low-temperature properties. It’s cheaper to buy than a full synthetic and affords better performance compared to a straight conventional oil.
There isn’t a set formula for synthetic blend oils. One may contain Group 1 or Group II base oils with a Group III, IV, or V synthetic. Another might blend a Group III and Group IV synthetic. It depends on the manufacturer.
Also, some synthetic blends may contain only 5% or 10% synthetic. Another brand might have 50% synthetic in its blend.
Synthetic Blend vs. Full Synthetic: Which Should You Use?
So, what’s the difference between full synthetic oil vs. synthetic blend? Is full synthetic better? It depends on the application. A full synthetic oil provides excellent low-temperature and high-temperature performance. It has great oxidation stability and many other performance advantages.
However, it may not be ideal for everyone. For example, some race car engine builders prefer a synthetic blend or conventional oil. They feel that a full synthetic is too slippery and doesn’t stay on the upper part of the engine (flat tappet, cam roller) as well. The mineral base in a semi-synthetic or conventional oil provides them with better clingability in those areas.
Cost is another factor. A synthetic blend oil is much less expensive than a full synthetic. You should look at what the OEMs recommend for your particular street vehicle.
Can You Mix Synthetic and Conventional Oil?
Yes. Mixing synthetic and conventional oil is fine. Years ago, there was concern about the esters used in synthetic oil. In most circumstances, you can add semi or full synthetic oil to your conventional oil. Check the label on the oil bottle because it will say if it’s mixable with conventional oil. Also, refer to your owner’s manual when in doubt.
Can You Switch Between Regular & Synthetic Oil?
What happens if you use conventional oil instead of synthetic, or vice versa? Can you switch between regular and synthetic oil? Not to worry. In most cases, you can switch between the two.
Before you do, check the label on the oil bottle to ensure that it’s safe. Also, be sure to refer to your owner’s manual. In the old days, there was concern that some synthetics weren’t compatible with mineral-based oils. That has changed over the years.
Suppose you’ve used conventional diesel oil for a long time. If you switch to synthetic, it might cause short-term leakage. Why? The thinness of synthetic oil and the additives used in the oil. Those additives might differ from your conventional oil. Synthetic oil can actually clean some of the engine deposits, which could cause leakage. It usually goes away.
Is Synthetic Worth It? Synthetic vs Conventional Oil Price
What are the disadvantages of synthetic oil? When it comes to deciding between synthetic vs conventional oil, there is another important point to consider: price. Full synthetic oil costs a bit more than a synthetic blend oil. It costs a lot more than regular conventional oil.
In fact, a 2017 survey of American Automobile Association (AAA) Approved Auto Repair facilities revealed some interesting information. The average cost of a conventional oil change was $38, while a synthetic oil change set you back $70 at that time.
For those that change their vehicle’s oil themselves, the average cost of 5 quarts of conventional oil was approximately $28, while synthetic oil was $45. In general, you will pay two to four times more for synthetic.
So, is synthetic worth it? Which is better, synthetic or conventional oil? It depends on the application. For passenger cars and trucks, full synthetic oil provides many advantages.
Full synthetic motor oil has several characteristics:
- It’s more highly refined
- It offers a naturally higher viscosity index
- It’s less prone to chemical degradation compared to conventional oil
- It provides better high-temperature protection and offers a longer lifespan than conventional oil.
Conventional engine oil eventually forms sludge from engine deposits. By comparison, a full synthetic oil resists sludge and deposit formation.
Many newer cars have tighter engine clearances. These tighter clearances need a lighter-viscosity (thinner) oil. Fully synthetic oil provides better low-temperature and high-temperature performance. This is even more important when using low-viscosity oil.
AAA also conducted research in 2017. It wanted to understand the differences between conventional and synthetic engine oils. Their lab tests showed synthetic engine oils outperformed conventional oils by 47 percent.
When debating synthetic vs. conventional oil, it’s always best to consult your owner’s manual and follow the OEM recommendations. Many auto manufacturers will void your warranty if you use an oil that they don’t recommend.
How Long Can You Go Without an Oil Change?
What about synthetic oil vs regular oil mileage? One thing is certain when comparing the two. Full synthetic by and large lasts longer under comparable conditions. For full synthetic, how long you can go without an oil change depends. How do you drive? Is it stop-and-go driving? Do you make a lot of quick trips that don’t allow the engine to reach full operating temperature?
Another key point is that while the base oil in a full synthetic tends to last a long time, the additives are a different story. They deplete over time because of both your driving habits and the condition of the engine. For instance, is fuel getting into your oil? Does your engine always run hot? Are your rings in good shape? Are you getting complete combustion?
Additionally, if you own a vehicle and don’t drive it often, change your oil at least twice a year, especially in November, before winter starts. Always keep fresh oil in an engine that doesn’t get used often. Fresh oil helps control rust or moisture thatcould form during the winter and get into your engine.
Some people like to change their oil every 3,000 to 5,000 miles because it gives them peace of mind. Our advice is to follow what your auto manufacturer recommends. If they say you can go 7,500 miles between oil changes, you’re safe to do so. That’s assuming you don’t drive under extreme conditions.
Where to Buy Motor Oil
With where to buy motor oil, there are many choices. VP has a full line of premium engine oils. We make motor oils for street cars, high-performance vehicles, high-mileage cars, and racing vehicles.
VP has blended industry-leading specialty fuels for nearly 50 years. We use the same innovative approach when designing our line of full synthetic, synthetic blend, and conventional motor oil.
VP engine oils give your vehicle maximum performance and world-class protection.
If you haven't already checked out part 1 of our mini series on engine oil, discover why oil viscosity is the most important physical property in engine oil.