The difference between synthetic and conventional oil

When it’s time for your car to get an oil change, if you find yourself wondering what the difference between synthetic and conventional oil is, you’re not alone. It’s important to note that not all motor oils are the same. Some are designed for high-performance engines or certain types of driving conditions, while others may be better suited for older vehicles. Cost is also a factor.

What is conventional motor oil?

Conventional motor oil, sometimes referred to as non-synthetic motor oil, is primarily designed to provide lubrication to the moving parts in the engine. Without sufficient lubrication, your engine is likely to run into mechanical difficulties and suffer from overheating, among other problems.

Not only does conventional motor oil help reduce engine wear and tear, but it contains additives designed to prevent the buildup of sludge, a jelly-like substance composed of engine oil, dirt and debris. Sludge in an engine has the potential to cause serious problems for your vehicle.

How is conventional motor oil made?

Conventional oil is derived from mineral oils that come from crude oil refinement. Through the manufacturing process, hydrocarbons within the crude oil are separated out and recombined to form the base oil. Additives, such as detergents and oxidants, are then mixed in.

How common is conventional motor oil?

Until synthetic oils became more widespread in the aftermath of World War II, conventional motor oil was the industry standard. Since then, the use of conventional motor oil has been steadily challenged by synthetic motor oils, particularly in new and high-performance cars. Nonetheless, non-synthetic motor oil remains widely used to this day.

What is synthetic oil?

Unlike conventional oils, synthetic oils are made in a lab using base oils that offer greater uniformity and stability at the molecular level. As a result, synthetic oils tend to last longer than their conventional counterparts. They resist wear and tear better and stand up to more extreme conditions than conventional oils. They also typically cost more, in some cases more than twice as much, though prices tend to vary significantly based on brand, quantity purchased and motor oil grade.

The rise of synthetic oil

Despite the higher price tag, the use of synthetic oils has grown in recent decades. This has positively impacted some routine aspects of car maintenance.

For instance, cars can typically go longer between oil changes than used to be the case. With synthetics, the days of changing your oil every 3,000 miles or so are broadly over. Unless you happen to drive in more extreme environments, you typically don’t need to change synthetic motor oil until somewhere between 5,000 and 7,500 miles, even longer with some synthetics. It’s important to note, however, that every car is different, and most manufacturers recommend changing your oil within a set interval regardless of how many miles you’ve driven. For guidance specific to your vehicle, it’s best to check your owner’s manual.

The superior lubrication of synthetic oil is also designed to help extend an engine’s life. This may help keep vehicles on the road for longer than was previously possible.

What is synthetic blend or semi-synthetic oil?

Synthetic blends are, as the name suggests, hybrids typically consisting of mostly conventional oil, with a percentage of synthetic oil blended in. These blends offer a balance of the performance associated with synthetic oil and the affordability of conventional motor oil. Like their counterparts, they help prevent sludge and extend engine life, while typically costing less than pure synthetics.

Conventional vs. synthetic oil

If you’re still wondering about the difference between synthetic and conventional oil, let’s break out some of the pros and cons.

Conventional oil pros and cons

Some of the pros for using conventional motor oil include:

• Typically costs less (sometimes significantly so) than synthetic oil.
• Possibly more suitable for use in some older vehicles.
• Still affords some level of protection to the engine.

Cons include:

• May struggle under harsh conditions, such as extreme heat or cold.
• Degrades faster than synthetics, which typically means more frequent oil changes.
• Calls for careful disposal (conventional motor oil is widely considered harmful to the environment if not properly handled).

Synthetic oil pros and cons

Some of the pros for using synthetic oil in your car engine include:

• Supports enhanced engine performance and tends to show greater stability in very hot or very cold driving conditions due to its higher viscosity index, meaning it typically flows more easily in extreme temperatures.
• Allows for extended drain intervals (meaning less frequent oil changes) under most operating conditions. (Exceptions may be if you regularly drive offroad, in high-dust environments or undertake heavy-duty towing.)
• Possibly offers a lighter environmental footprint, if only because it typically requires fewer oil changes.

Some of the cons include:

• May cost significantly more than conventional oil.
• Potentially slightly lower fuel economy for highway driving.
• Not always necessary, depending on the type of car you drive and the typical conditions you drive in.

These are some of the main differences between regular and synthetic oil, though determining the right oil for your car will depend on a range of factors specific to your vehicle and how you drive it.

Checking your owner’s manual

It’s best practice to check the owner’s manual for the manufacturer’s recommendation on the type of motor oil that’s best suited for your car.

Ultimately, whether your car uses conventional or synthetic motor oil may not even technically be a choice. Nowadays, many newer cars require the use of synthetic oil rather than conventional motor oil. In other cases, conventional motor oil may be specifically recommended by the manufacturer.

Consulting your mechanic

Asking your mechanic for advice on which engine oil to use may also be a good idea. Your mechanic may recommend you switch from one type of oil to another due to some of the potential benefits listed above.

In summary

Perhaps the most obvious differences between synthetic and conventional oil are cost and performance, as is the impact of the oil on the engine’s longevity. While older cars are typically designed for conventional oil, newer models tend to favor synthetic for some of the reasons you explored above. The best way to determine which engine oil is right for your car is to consult the recommendations in your owner’s manual, but your mechanic should also be able to advise you.