Oil performs the vital function of lubricating your auto’s engine, so it’s a good idea to choose the right oil for your vehicle.

Two main types of engine oils exist – conventional and synthetic. Understanding the differences between these two oils will help you answer confidently the next time you have your car serviced and the auto technician asks what type of oil you want in your car.

Conventional oil

Conventional oils are mineral-based and created from naturally occurring crude oil that has been removed from the earth. These oils are formulated with special additives to ensure that they possess just the right heat tolerance and viscosity, the latter of which refers to thickness and the ability to flow.

Conventional motor oils usually cost half the price of synthetic motor oils, but need to be replaced more often.

Synthetic oil

In existence since the 1970s, synthetic oils often have a conventional oil base, but as their name suggests, they’re created in a chemical plant with chemical compounds. Synthetic oils are engineered to provide the highest level of lubrication in temperature extremes. Such oils also have built-in cleansing properties that lead to a cleaner engine.

A recent independent evaluation of motor oils by AAA found that synthetic oil outperforms conventional oil by an average of almost 50 percent. You do pay a price for this superior performance. Synthetic oil costs twice as much as conventional oil.

Which oil to choose for your car?

Synthetic oils are durable and generally last two to three times longer. They’re also thinner and resist temperature extremes. When you use synthetic oil, you require less frequent oil changes than when you use conventional oil.

Synthetic oil may also be ideal for your car if you drive in conditions that involve stop and go traffic, hot and cold temperature extremes or short trips.

On the downside, synthetic oil is substantially more expensive than conventional engine oil.

High mileage oil

High mileage oil is designed for vehicles with more than 75,000 miles. Such oil features additives that help protect seals. This leads to less leakage and oil burn-off, which can be common in older cars. If your vehicle is high-mileage and high performance, it’s suggested that you go with this type of synthetic oil.

Not every car requires synthetic or high mileage oil. To determine which type of oil is best for your vehicle, check your owner’s manual or ask your auto technician.

As a rule of thumb, most new cars require synthetic oil. Older cars generally run well with conventional oil, unless your vehicle has more than 75,000 miles on it, in which case high-mileage oil is recommended.

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