Synthetic vs conventional oil — what’s the difference?
While synthetic engine oil contains fewer impurities and provides better protection than conventional oil, both these engine lubricants have their benefits.
In this article, we’ll discuss the major differences between synthetic and conventional oil— how they’re made, prices, and oil change intervals to help you understand each motor oil better.
This Article Contains
- Synthetic vs Conventional Oil: 4 Key Differences
- Benefits of Synthetic vs Conventional Oil
- How to Pick the Right Engine Oil for Your Vehicle?
Synthetic vs Conventional Oil: 4 Key Differences
Synthetic engine oil and conventional oil are used to lubricate engine parts.
These oils also perform other functions like:
- Protects engine parts against engine wear and tear
- Slows down water damage and corrosion
- Prevents engine sludge
- Removes and prevents engine dirt and impurities from interfering with engine functions
- Cools down engine parts when they reach high temperatures
- Transmits engine torque for maximized horsepower
Despite similar functions, synthetic and conventional engine oils also have some key differences:
A. How They’re Made
Both synthetic and conventional engine oils are made from crude oil, but each process’s quality and complexity vary greatly:
1. Synthetic Oil
Synthetic oil is chemically produced in the laboratory by refining crude oil to get a synthetic base oil — to which various additives are added, like castor waxes and paraffinic oils.
The base oil is synthesized by rearranging hydrocarbon molecules. These synthetic base oil molecules are uniform in shape with fewer impurities between them — resulting in a highly reliable motor oil with improved stability to the oil’s structure under higher temperatures and pressures.
2. Conventional Oil
Conventional oil is obtained by heating crude oil at various high-temperature points — leaving behind a heavier base oil. This acts as the base for conventional motor oil.
Certain additives are added to this base oil for increased performance and engine protection. Although conventional oil protects against friction and engine wear, it’s less refined than synthetic oil.
B. Oil Viscosity Index
The viscosity index (VI) for conventional oil is 95 – 100, whereas, for synthetic oil, it’s above 120.
Synthetics have a naturally higher VI than conventional oil because of their additives. The higher viscosity of synthetic oil makes it capable of withstanding extreme temperatures and pressures without getting affected.
But this doesn’t mean all synthetic oils work for all temperatures. If you’ve noticed, every motor oil bottle has an American Petroleum Institute (API) label printed on it. This label explains the viscosity and performance index of the oils.
C. Pricing Differences
Conventional motor oil (mineral oil) is much cheaper than fully synthetic oil.
To give you an idea, synthetic motor oil can cost you about two to four times more than conventional oil. For example, five quarts of conventional oil cost about $28, while the same amount of synthetic oil is around $45.
That’s because producing synthetic engine oil is costlier than other motor oil types, as synthetic oil requires advanced technology and equipment. This means that it can also be expensive to maintain a regular synthetic oil change schedule.
As a result, most people often shift to synthetic blend motor oil (or semi synthetic oil), a combination of fully synthetic and conventional oil. This cheaper alternative to synthetic oil performs better than mineral oil. A synthetic blend also acts as a stepping stone when switching to synthetic motor oil.
D. Oil Change Interval
An oil change is crucial to maintaining engine performance.
Let’s see how the two oils differ in this aspect:
1. Synthetic Oil
While synthetic oil does cost more, it also has a longer oil change interval.
Most vehicle mechanics and manufacturer manuals recommend getting a synthetic oil change every 5,000-7,000 miles. However, it can go as long as 10,000 to 15,000 miles if you follow good driving practices like:
- Regular oil top-ups
- Oil filter changes
- Good braking habits
- Using quality motor oil
2. Conventional Oil
Conventional oil, on the other hand, has a more frequent oil change interval compared to full synthetic and synthetic blend oil.
You can expect about 3,000-5,000 miles from your traditional oil. In best-case scenarios, it can go for about 7,000 miles without needing an oil change service.
Once your mileage exceeds the oil change interval, you’ll start experiencing signs of bad motor oil. If you notice dark, muddy oil with suspended impurities, you may have expired oil.
Then, does this mean that synthetic oil is better than conventional oil?
Benefits of Synthetic vs Conventional Oil
While both conventional and synthetic oils have their advantages, synthetic oil outperforms regular oil in most cases.
Let’s take a closer look at the benefits each type of motor oil offers.
1. Benefits of Synthetic Oil
Synthetic oil is great for several functions, including engine protection at extreme temperatures.
Here are some other benefits of synthetic motor oil:
- Produces fewer emissions than regular oil
- Less frequent oil change intervals
- Better engine protection against engine wear due to a higher oil viscosity and fewer impurities
- Greater resistance to oil thickening
- Better stability at low temperatures and high temperatures
- Maximized horsepower for engine parts due to their high resistance to friction
- Improved gas mileage
Some potential synthetic motor oil disadvantages are:
- Higher costs (though its longer oil change interval might offset this)
- Possible additive separation at cold storage conditions
- Slightly lower gas mileage at highway speeds
2. Benefits of Conventional Oil
Conventional motor oil may not be as refined as synthetic oil, but it still has a couple of advantages over the latter, like:
- More cost-effective than synthetic or synthetic blend oil
- Has more affordable oil change intervals
- Better suited for cars with an older engine that requires thick motor oil viscosity grades
- Less likely to cause leakage and engine wear in an older car
Here are the downsides of using traditional oil:
- Prone to oxidation and degradation
- Doesn’t perform well in cold temperatures
- Prone to collecting sludge in new vehicles
- Highly toxic extraction process
So how do you choose the right motor oil for your car?
How to Pick the Right Engine Oil for Your Vehicle?
Choosing between synthetic and conventional oil isn’t as easy as you think. There are some essential aspects that you need to consider.
Let’s see what they are.
1. Synthetic oil
Most modern engines, especially turbocharged engines, come equipped with synthetic oil.
If your car originally uses conventional oil, you can swap it out for synthetic. But whether it’ll work or not depends on your driving habits and conditions.
You can choose synthetic motor oil:
- If the engine has a relatively high daily performance (driving long distances, frequently towing heavy loads)
- If you’re living in extremely hot or cold temperatures
- If you own new vehicles with turbocharged engines
2. Conventional oil
Although a car with an older engine is more suitable for conventional oil, switching to synthetic is also possible.
But sometimes, switching to synthetic oil isn’t the best option.
- If the engine has low performance requirements (day-to-day driving)
- If you drive an older car with high mileage (75,000 miles and above)
- If the car has been poorly maintained
If you’re still confused, you can try another option — to alternate between synthetic and conventional oil. Or you can also try semi synthetic oil for your engine.
Synthetic blend motor oil is cheaper than synthetic oil but performs much better than mineral oil. It also helps increase gas mileage and fuel economy. Plus, with proper maintenance, a synthetic blend can last almost as long as fully synthetic oil.
Whether you choose a conventional, synthetic, or synthetic blend motor oil type, remember to refer to your vehicle’s owner’s manual to ensure it’s the right oil for your car.
Synthetic motor oil offers more advantages than conventional oil because of its synthetic additives and better viscosity. It‘s more effective in protecting your engine and provides far better performance for modern engines.
Even so, it’s best to consult your owner’s handbook to choose the right oil for your vehicle. Also, don’t forget to get routine car maintenance to keep your vehicle in good shape and optimize fuel economy.
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