“Why should I pay more for synthetic oil?” The confusion over synthetic oil vs. conventional oil is understandable.
The mechanic has looked over your car. Then, he said something about engine sludge, oil filters, and asks when you last changed your oil. Even though you may not know the exact date, you remember seeing low prices on plastic banners. Now, the world of oil changes feels like snake oil sales. Synthetic oil? It’s not an oil alternative. It’s a man-made oil. Ecologically, it produces fewer emissions. It is more expensive at six to ten times the price. But, it is also a better oil.
So, why choose synthetic over conventional oil?
What is Synthetic Oil?
Synthetic oil is nonetheless oil, though it is somewhat man-made. Synthetic oil is made from a base oil, powder additives, and a carrier oil that enforces an even distribution of the additives.
Both synthetic oil and traditional motor oil are made from refining oil. Most synthetics begin with highly refined crude oil, pumped from deep underground. That is the same source as conventional oil. Other synthetic oils use artificially made compounds or a synthetic oil as a base oil. The primary difference between synthetic oil and traditional oil is at the level of refinement.
The base oil falls into one of several “oil grades” from mineral oils extracted from crude (Group I and II) to fully artificial, compound-based oils (Group V). All grades of oil are manufactured with additives that increase performance.
Refinement processes and ingredients also result in scientific control over molecular size and purity. That can lower friction, reduce engine sludge, and increase performance.
Synthetic oil technological advantages include:
- Uniform molecular size means less friction
- Refinement and engineering reduce deposits
- Additives boost protection and can clean engines
- Better function in cold and extreme weather
- Cleaner oil with fewer impurities
Synthetic oil was first developed in 1929. With technology and access to resources, it has refined to accommodate jets, high-performance vehicles, and everyday consumer vehicles. When Allied Forces imposed oil shortages on Germany during The Second World War, for example, Nazi Germany pushed for man-made oil to fuel their military. During the 1970s American Energy Crisis, there was an enormous effort to improve fuel economy by creating better synthetic oils.
The need for synthetic oils also comes from technological changes. High-performance vehicles and machinery—from jets that break the sound barrier to industrial plants—have to operate in extreme conditions and temperatures. Highly refined engine oil allows better temperature resistance.
Full Synthetic Oil
Full synthetic oil is the purest type of synthetic oil. However, there is no global standard that grades synthetic oils. Each manufacturer has its own secret ingredients and processes. Thus, the term “full synthetic” is just a marketing term.
For the most part, the kind of synthetic oil found in the United States for your household vehicles is likely in the synthetic oils that use a Group III base. That means that the full synthetic you get from your auto store is not really full synthetic. Group III is a highly refined mineral oil made. The mineral oil is refined beyond simple extraction through a process called hydrocracking.
Full Synthetic vs. Synthetic Blend
Full synthetic oils are better understood as a grade of motor oil. Semi-refined--also called synthetic blend--oils are less refined than full synthetic oil. Semi-synthetic oil blends traditional oil with the more technologically advanced oils. You get the advantage of additives and more refinement. But, the impurities and inconsistent molecular size of conventional motor oil are still in the blend at lower degrees.
The benefit of synthetic blends is largely a cost-vs-benefit decision. Synthetic blends are cheaper than full synthetic motor oil but higher performance than conventional oil.
Synthetic Oil Change Interval
Because synthetic oil is better on your engine and has fewer impurities, it can go longer than conventional oils or synthetic blends.
Schedule regular intervals. For conventional oil, twice a year is suggested as a safe way of keeping track. If you want to keep better track, every 7,500 miles is suggested for average cars. You should also change your oil filter every oil change. But, especially if using synthetic oil, every other oil change is sufficient if you don't regularly push your car hard or endure extreme conditions.
Check your owner's manual. Newer cars may be able to go 10,000 miles or only need an oil change once a year. Turbo engines and older cars may still require oil changes every 3,000 to 5,000 miles.
Synthetic oil change intervals range 10,000-15,000 miles or once a year (whatever comes first). Extended performance synthetic motor oil is on the upper top of that range. That extra 5,000 miles may be worth the investment.
Synthetic Oil vs. Conventional Oil
Visually, you cannot tell the difference between new synthetic and conventional oil. There are two major differences, however. First, how they are made is a distinction. We've explained that synthetic oil is far more refined than conventional oil.
Second, the way they run in your car is worlds apart. Used motor oil shows a lot thicker and sludgy in conventional oil vs. synthetic oil, given the same amount of wear. Synthetic oil is by far better for performance. It protects the engine due to lower levels of friction. Additives help clean the engine of deposits. And, fewer impurities mean it burns cleaner, thickens far more slowly, and has fewer deposits to start.
"According to industry tests, synthetic oil engines perform 47% better than engines using conventional motor oil." - AAA
The benefits of synthetic oil vs conventional oil:
- Fewer emissions
- Better fuel and oil economy
- Increased engine protection and wear from lower friction
- Longer intervals between oil changes
- Reduced engine drag from greater resistance to thickening
- Oil effectiveness/quality is more predictable and uniform
- Better all-weather protection
- Quicker engine start time
- Helps clean engine sludge and deposits
Synthetic oil is generally considered the best oil. It is designed for performance. However, that same manufacturing process makes it more expensive.
The general belief in what type of oil is best is:
- Best = Full Synthetic Oil
- Better (than full mineral motor oil) = Synthetic Blend
- Good = Mineral Motor Oil
Notice that there is no “bad” motor oil. Check with the owner’s manual of your vehicle to see their suggestions.
The real deal of synthetic oil vs. traditional oil:
- Better gas mileage won’t be an obvious difference to your short-term budget
- The added engine protection may save costs overall
- Synthetic oil is 6x – 10x the cost of traditional oil
- Switching to synthetics can clean deposits that are plugging leaks (You really shouldn’t have bad seals in the first place)
- You can switch back and forth between synthetic and traditional oil without consequence
- All cars benefit from the additives in synthetic oils
How to Choose the Best Motor Oil for Your Car
If you can afford it, choose a full synthetic oil. It is the best oil for any engine. Synthetic oil cuts down the hassles or oversights related to more frequent oil changes and deposits.
If synthetic oil is too expensive, go with a blend or rotate between a full synthetic and non-full synthetic every other oil change. Changing car oil will not damage your vehicle. Keep a record to remember the mileage, next oil change date, and type of oil.
Refer to your owner’s manual or look up the:
- Viscosity grade
- Oil specification
Your mechanic, oil change service, or auto parts store associate will be able to provide advice on the best oil for your specifications.