Synthetic Oil vs. Conventional Motor Oil: Understanding the Difference

Toco Joe from Toco Warranty explaining the difference between synthetic and conventional motor oil

Understand the pros and cons of synthetic and conventional oil so you know what to put in your car.

If you don't have a lot of experience with how cars work, figuring out whether to use synthetic oils or conventional motor oil can be a little confusing. Here's what you need to know to make a smart decision for your vehicle.

What Oil Does in an Engine

Oil is in your engine for an important reason - it lubricates the metal pieces that are moving at high speeds while you're driving. Without motor oil, your engine parts will grind together and eventually seize up. Running an engine dry can seriously damage your engine.

Synthetic and Conventional Oil

While the type of oil in your engine is less important than whether there's oil in there at all, it's still important to determine the best type of oil for your vehicle. Manufacturers often include instructions on the specific oil weight and viscosity to use, but they may not tell you whether synthetic oil or conventional motor oil is preferred.

The first important thing to know is that synthetic oil can be used in any engine - which means it's safe to switch to synthetic oil and it's not going to harm your engine. So what's the difference? It really comes down to cost and environmental impact, as well as some little differences in how you maintain your car.

Long-Lasting Oil

Another important thing to note is that synthetic oil lasts longer - so you can go longer between oil changes. You've probably heard the rule that you should change your oil every three months or 3000 miles. However, the rules for synthetics are different than the rules for conventional oil. For synthetic oil, the recommendation may be every six months or 5000 miles. You might even see some manufacturers call for oil changes every 7500 or 10,000 miles. Always check your owner's manual to verify your vehicle's recommended oil change schedule.

Synthetic oil lasts longer because it’s more resistant to high temperatures and less prone to breaking down. Over time, conventional crude oil-based motor oil can get gritty and grimy and develop sludge in the engine. Synthetic oil, on the other hand, is more durable because it's made from synthetic chemicals. For this reason, mechanics might suggest synthetic oils for high-performance vehicles or vehicles that operate under heavy loads.

There's also the environment to consider. Longevity is also the biggest environmental argument for synthetic oil. Both synthetic and conventional oils are made from petroleum, so it’s a “lesser of two evils” type of decision, but because synthetic oil gets changed less, there’s much less waste.

How to Decide What’s Right for Your Car

The general consensus is that you should use synthetic oil for high-performance cars, newer cars, or vehicles that you want to invest more money in.

For older cars, you may want to stick with conventional motor oil - since, with a vehicle that is well past the 100,000-mile mark, you simply have different priorities. You're not as concerned about maximum performance or long-term investment as you are about keeping the car on the road.

In addition, older vehicles often start to either leak or burn oil. In these cases, having synthetic oil and waiting longer times between oil changes can actually work against you as the vehicle owner. It's easy to forget to check the dipstick for a while, and as the oil level gets lower, it puts much more stress on the engine.


If you don't have an older vehicle, the only big negative to synthetic oil is the cost. A synthetic oil change can run you a few dollars more than conventional oil, which is one reason why some drivers might be reluctant to switch. Otherwise, synthetic oil really is superior, and it's going to be the oil of choice for late-model vehicles and what's due to come off manufacturing lines in the future.

With hybrids and electric cars increasing in popularity, there's a chance that gasoline engines may go the way of the dinosaurs. But for now, it's still very much what's on the road, and knowing the difference between types of motor oil is an important part of vehicle ownership and maintenance.