Conventional vs Synthetic Blend vs Full Synthetic Oil (Which to Use?)

Choosing the right engine oil type for your car engine can be difficult without knowing much about the different types. Here are the differences between synthetic blend, conventional and full-synthetic motor oil

Conventional Vs Synthetic Blend Vs Full Synthetic Oil

Getting an oil and filter change is one of the most basic maintenance tasks you can perform to your vehicle.

While the majority of auto enthusiasts know how to change the oil, choosing the right type can often cause confusion. How do you know which to use – conventional vs. synthetic blend vs. full synthetic oil?

Conventional oil is a cheaper choice for vehicles that do not require extra protection and performance, usually made for older vehicles. Full synthetic oil has been engineered to meet the highest standards of performance and protection. A synthetic blend is a mixture of conventional and full synthetic oil.

While each type of oil has its own benefits, there are specific reasons to choose one over another in certain applications.

We look at the differences between these types of oil and discuss which is appropriate for various applications. 

What is Conventional Oil?

Engine Oils

Conventional oil is the type that has been around the longest. It is time-tested and shown to protect most vehicles in normal driving conditions.

The conventional oil comes from crude petroleum, designed to keep the engine clean from contaminants while minimizing moisture and improving the lubrication. All major brands manufacture conventional oil, so it is easy to find. 

However, conventional oil might not provide the best fuel economy and it can allow carbon or sludge buildup over time. That’s why it’s important to change this type of oil more frequently. 

What is Synthetic Blend Oil?

Synthetic Blend

Synthetic blend oil mixes full synthetic with conventional oil to combine the best of two worlds. While it contains some conventional oil, there are also some additives, such as those found in synthetic formulations.

You can expect a slightly better performance from this oil without spending top dollar. However, it’s difficult to determine how much of the synthetic formulation is added to the petroleum base because the ratio is different between brands. 

In general, the synthetic blend is going to offer better fuel economy than conventional oil but won’t perform as well as full synthetic. Additionally, you will receive slightly better protection from carbon and sludge than if you choose conventional oil.

What is Full Synthetic Oil?

Full Synthetic Oil

Synthetic oil has been manufactured with special additives, causing it to be the most expensive of the three options. While there are no set standards about the refining process, you can guarantee better performance than compared with conventional oils.

Some synthetics are still made from the petroleum base, but it is extremely modified to provide high-performance qualities. You can find manufacturers that use the natural form and tweak it with special additives, while others will create the entire formula from manufactured compounds. 

Full synthetic oil has a lower viscosity than conventional oil. Because of less friction, fuel economy is improved and more power can be unleashed from the engine. You can also use most synthetic oils in any climate, providing superior cold starts and great lubrication in the summer. 

RELATED: 10 Best Synthetic Motor Oils

Finally, synthetic oil doesn’t break down the same way that conventional oil does. For this reason, the changing interval is longer, allowing you to perform oil changes less frequently. 

When choosing synthetic oil, you have to take a look at the formulation as each manufacturer does it differently. You can find varieties with detergents, corrosion inhibitors, anti-foaming agents, dispersants, anti-oxidants and viscosity index improvers. 

Choosing the Right Motor Oil

Always check your repair manual to use the right motor oil with the correct specs in your car engine. Using the wrong engine oil type can damage your engine and the warranty may not cover it.

1. Cost

If you need to save some cash, conventional oil might be your top choice. One quart might cost you as little as $3. You can also choose conventional oil from any of the top manufacturers.

At the other end of the spectrum, full synthetic is going to cost the most. You can expect to pay a minimum of $8 per quart. Of course, buying it by the gallon will help you save a little dough.

The best option for most people is to choose a synthetic blend instead. It’s slightly more expensive than the conventional, at about $4-7 per quart, but it offers some of the benefits of the costly options. 

2. Changing Intervals

Conventional oil is going to break down faster than any other type. That’s why conventional oil changes must take place every 3,000 miles in most vehicles. While the cost is low for the oil, when you look at the per-mile expense, it no longer seems like much of a bargain.

Some synthetic oil is rated for up to 15,000 miles of use. However, this recommendation doesn’t take into account how long the oil filter is rated for, so that’s something to consider. Many people running a synthetic blend or full synthetic prefer to change their oil between 5,000 and 10,000 miles. 

3. Protection

There’s no question that synthetic and blends are going to protect the engine over the long haul. Conventional oil simply doesn’t have the additives to perform at the same level. 

With that in mind, is synthetic oil better than a blend? Both motor oils are going to provide protection, ensuring that the engine gets what it needs. However, full synthetic is more efficient. You can expect a more calibrated formula designed for your driving purposes. At the end of the day, it comes down to deciding how much you are willing to spend to protect your vehicle’s engine.

Magnus Sellén
Written by:

Magnus is the owner and main author of Mechanicbase. He has been working as a car mechanic for over 10 years, and the majority of them specialized in advanced car diagnostics and troubleshooting. Certified Automotive Diagnostic Technician.

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