Synthetic Versus Conventional: Which Motor Oil is Best?

Which motor oil is the best?

As the lubricant for the moving parts of your engine, motor oil is widely considered to be the most important fluid you can use. It prevents excessive engine wear and tear, which makes it vital to keep your car running. So when the time comes to get under the hood do an oil change, you can bet you’ll want to know whether to buy synthetic or conventional oil.

What You Need to Know
There are three main types of oil – conventional, synthetic and synthetic blend. Conventional oil is organic—it’s essentially refined crude oil that’s been pumped up from the ground. Synthetic oil is manufactured molecule by molecule, and because of that, synthetics have fewer imperfections in their chemical buildup than conventional does.

In general, synthetic oil outperforms conventional oil on all counts:

  • Synthetic oil works better in extreme temperatures from below freezing to above 100 degrees Fahrenheit. Conventional oil is highly reactive to temperatures.
  • Because synthetics have superior lubrication (they’re more slippery), they give you better fuel economy, performance, and even a longer engine life.
  • And best of all, synthetics don’t have to be changed as often. But make sure you meet warranty service mileage intervals regardless.

The only downside to synthetic oil is it costs more than the regular stuff. But before you choose pennies over performance, crunch the numbers—with longer oil change intervals, the price difference might be a wash.
Synthetic blends, or “semi-synthetics”, add synthetic additives to conventional oil and can be a nice compromise between the two. They’re less expensive but provide some of the performance enhancement you get from a synthetic.

These three types of motor oil will work fine in your vehicle as long as they meet current American Petroleum Institute (API) certification and don’t go against the manufacturer’s recommendations. The only type of engine you should never use synthetic oil in is a rotary. Rotary engines have unique seals that are engineered for use with conventional oil only.

Pro Tip: Check that you’re not voiding your warranty by using the wrong oil. Many newer vehicles require that you use synthetic oil and some synthetics aren’t approved for certain diesel engines.

The Final Say

When buying oil for your car, the best thing you can do is to follow your manufacturer’s recommendations. So, check that owner’s manual! When you consider that the wrong oil can cause an engine to fail, it pays to take their suggestions seriously. If you have the option to choose between synthetic and conventional and still aren’t sure which to pick, consult a pro—they’ll know what to do.

Seasons change…and so should your oil

Out here, most people have more than one vehicle, and we’re not just talking about cars and trucks. Lawn mowers, farm tractors, ATV’s, boats, log splitters, and personal watercraft – the one thing they all have in common is an engine. Each year, when I say goodbye to a long, hot summer, I like to reward my machines for the reliable performance they’ve delivered at work or play, and get them ready for the winter that’s ahead. I start by giving them all an oil change.

It’s a great time to do it—the grass isn’t growing as fast, the garden’s about done, so I’m spending less time weeding, and it’s still slightly too warm to cut wood. To maximize my time, I try to do all of the oil changes on the same weekend. One of the benefits to doing it this way is that I can collect all the old oil at once and take it somewhere that offers free automotive oil recycling. There are countless resources and videos out there that show you how to change your oil. It’s actually pretty easy. Maybe the hardest part is figuring out what’s the best motor oil for your needs and where you stand on the synthetic oil vs. regular oil discussion.

Automotive Oil RecyclingFor me, the best motor oil is the one that’s going to protect my engine. My only two rules are that I always follow the vehicle or engine manufacturer’s recommendation for oil weight, and I always choose oil with the API (American Petroleum Institute) symbol. It means the oil meets API quality standards. As for the synthetic oil vs. regular oil debate and the common question, “Is synthetic oil worth the cost,” I think it is. The best synthetic motor oils are supposed to provide improved performance and engine protection. Consider this info from Mobil 1 website: “Conventional oils lack the performance of synthetic oils in the areas of low-temperature performance and high-temperature oxidation stability.” Most of my engines have a lot of miles or hours on them, so I choose synthetic oils, hoping to keep them healthy and see me through the winter.

For those of you out there with lots of toys, make sure to change your engine oil at the recommended manufacturer intervals. It’ll help prolong life and prevent further problems down the road.

Editor’s note: Advance Auto Parts is here to help you learn more about which engine oil works best for your car. You can also recycle your used motor oil at most Advance Auto Parts store locations.