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.

Motor Oil: What Do the Numbers Really Mean?

Our Mechanic Next door delves into the origins and meaning of motor oil viscosity grades.

“220. 221. Whatever it takes.”

motor oil 1

That infamous line of reasoning worked for Jack Butler (Michael Keaton) in the 1983 movie Mr. Mom, so it should work for you, too, when it comes to selecting the right motor oil grade, right? Simply pick a number? Nope! Just like with electricity, when it comes to car oil, numbers matter – especially if you want to protect your engine.

Oil “weights” or grades – such as 10W-30 – are actually a numerical coding system developed by the Society of Automotive Engineers (SAE) to grade oils based on their viscosity.

Viscosity is measured by the how long it takes a specific amount of oil to flow through a specific-sized opening at a specific temperature. The longer the oil takes to flow through, the higher the viscosity. The tool used to conduct that test is a viscometer.

Think of pouring pancake syrup from the bottle – at warmer temperatures, the syrup pours fast and easy, while at colder temperatures, it’s thicker and more difficult to get flowing. The same can be said for engine oil.

The particular challenge with motor oil, however, is that automotive engines need engine oil to be both thin and free flowing when temperatures are freezing and the engine is cold, but thick when it’s hot out and the engine has reached operating temperature. That’s where multi-weight or multi-grade oils enter the picture and why they were created.American Petroleum Institute

SAE’s J300 standard, first published in 1911 and revised numerous times since, classifies oil into 11 viscosity grades – 0W, 5W, 10W, 15W, 20W, 25W, 20, 30, 40, 50, and 60 – with the “W” signifying “winter,” not weight. Oils first received this “W” designation from SAE in the 1950s. The lower the number preceding the W, the lower the temperature for which the oil is rated. Those winter numbers were modified further after a rash of catastrophic engine failures in the early 1980s. Unusually cold weather in the U.S. and Europe caused oil to gel. When this occurred, the engine would still start, but it couldn’t pull the gelled oil out of the oil pan, resulting in the failures. As a result, SAE added a low-temperature test to measure pumping viscosity as well, and indicated this oil with the W specification.

Back to the idea of multi-weight oils. A popular oil, such as 10W-30, performs like two oils in one when it comes to engine lubrication. At colder temperatures it is and delivers a 10W-grade oil performance, while at higher temperatures it is and performs like a 30-grade oil – according to SAE’s standards and tests – providing engine protection at both ends of the temperature spectrum, which is important since engines have to operate in a range of temperatures. Think of it this way – that SAE 30 oil you might use in your riding mower has the same viscosity as the 10W-30 oil in your vehicle, but only at 210°, the maximum temperature that SAE requires. The difference arises at colder temperatures where the SAE 30 oil can’t perform, necessitating some enhancements that make it a multi-grade oil. At those lower temperatures, that’s where the 10W oil and its characteristics come into play.

Oil’s desired performance characteristics at varied temperatures, as specified by SAE, are achieved through the addition of Viscosity improvers (VI) or modifiers that increase the oil’s viscosity as temperatures rise. The result is oil that performs and provides engine lubrication no matter what the temperature.

The good news for drivers is that they don’t need to be an engineer or chemist to know which car oil to use, and they don’t have to change their oil grade whenever the temperature changes. Simply follow the motor oil grade recommended by the vehicle manufacturer for optimal engine protection in all types of weather.

oil sealIt’s important to note that SAE also has a coding system for gear oil, such that used in a manual transmission, and that it’s different than the ratings for engine oil. So if there’s a bottle of 85W-140 oil sitting on the barn or garage shelf gathering dust, don’t put it in your engine.

And finally, when choosing an oil, look for one with the American Petroleum Institute “donut” seal on the bottle. It indicates that the oil meets API performance standards.

A common sense guide to keeping your engine oil fresh

If you asked the good folks in my neighborhood how often they’re supposed to change their oil, I guarantee you they’d all give the same response: “Every 3,000 miles.”

And if you followed up by asking them what motor oils their cars require, how many quarts of oil their cars take, and which motor oil brandsare the best, I guarantee you’d get a lot of blank stares.

oil changeThat’s because most people in this country believe the myth that every car needs an oil change every 3,000 miles. And once they drop the car off at the garage, they trust that the mechanics on duty will get all of the details right.

In fact, most cars can safely go far more than 3,000 miles between changes. And when it’s finally time for an oil change, you should know just as much about what your car needs as a knowledgeable mechanic.

Debunking the 3,000-Mile Myth

I’m not sure how this one got started, but it has sure put a lot of big oil executives’ kids through college. Listen, you can either trust the mechanic who suggests the same 3,000-mile interval to every single customer, or you can consult the service schedule in your owner’s manual and trust the people who built your car.

I know people who build cars, and they design their vehicles to withstand far more stress than the service schedule allows. So if your owner’s manual recommends an oil change every 7,500 miles, rest assured that your engine is designed to go even longer on a batch of oil without missing a beat.

Trust me on this one. Don’t worry about draining perfectly good engine oil every 3,000 miles. Only change it when your car’s engineers say you should.

Knowledge is Power

Here’s what I do every time I go in for an oil change, and I recommend you do the same.

1. Know Your Viscosity

Viscosity is that funny combination of numbers and letters you see on a bottle of engine oil. 5W-30 is a common one; so is 10W-40. It basically refers to how easily the oil flows at different temperatures. Consult your owner’s manual for the recommended viscosity, and double-check with your mechanic that he plans to use it.

2. Know Your Car’s Oil Capacity

Find the page in your manual where oil capacity is specified. It will probably be in the neighborhood of five quarts, although some specialized engines can take eight or more. Keep that number in mind, and ask your mechanic how many quarts he’ll be putting in. It’s a good way to guard against overfilling, and also to make sure your mechanic’s on the ball.

3. Choose a Quality Engine Oil

I’ll give you a couple options here, depending on how involved you want to get. At a minimum, you’ll want to ask your mechanic about his motor oil brands of choice, and why. All motor oils are not created equal; you should only use motor oils with the American Petroleum Institute’s seal of approval. You might also want to read up on the benefits of synthetic oil and mention that, too. And if you’re a real stickler like me, hey, don’t be afraid to buy your own oil and bring it to your mechanic. That’s the best way to ensure that a high-quality product is keeping your car’s heart beating.

Editor’s note: If you do your own car maintenance, you can save even more with Oil Change Specials from Advance Auto Parts. Advance will also recycle your used motor oil free of charge—at one of more than 3,500 stores. (Most locations, unless prohibited by law.)

 

The importance of Engine Oil: the sweet fluid that keeps your car running smoothly

I work a lot of long hours. I start early and often finish late, and as anyone around me (particularly my wife) knows, I drink a lot of coffee. It’s the sweet black elixir that keeps me going and helps me through the day.

image of engine oil

Speaking of precious elixirs (You were waiting for that, weren’t you?), engine oil—commonly known as motor oil—is the same thing for cars. Your car’s engine is a series of complicated, hot, fast-moving parts, and engine oil is what keeps all those parts lubricated and running smoothly. As the parts heat up, so does the oil, so it’s very important to have the right type of motor oil, in the right amount, and keep it changed regularly.

The bottom line is, pay attention to the specifications in your owner’s manual and you’ll be happier than my wife during a sale at Macy’s. Buy the correct type of engine oil, in the correct weight. Some manufacturers specifically recommend synthetic motor oil, and if you use a different kind, it could void your warranty. Weight has to do with the temperatures in which you run your car (winter or summer) and also how thick the oil becomes when heated. Bear in mind that you don’t want it too thick when it’s cold or too thin when the engine heats up. This is particularly important in new cars, where the tolerances (gaps between moving parts) can be extremely thin, so you want to make sure the oil isn’t thicker than recommended.

If you’re committed to a lot of do-it-yourself jobs, changing your own engine oil is very easy and relatively painless (although it can get really messy) but even if your mechanic changes your engine oil as a part of your regular service, it’s never a bad idea to keep a quart in your car and do a quick check of your oil levels when you fill your tank up…just be careful, as your engine gets VERY hot and its really best to check oil when the engine is cooler. So make gassing up and checking oil your first stop.

Just make sure the motor oil quart has certification on it from whatever your manual recommends: likely the SAE (Society of Automotive Engineers) and preferably the API (American Petroleum Institute). They regulate and make sure the oil is of good quality and thickness.

The bottom line is, your car needs engine oil the way you need water (or I need coffee). It’s very easy to keep an eye on the engine oil and change it regularly for many years of happy, reliable engine life. Happy motoring.

 

Editor’s Note: Advance Auto Parts can assist you in finding the optimal engine oil, plus all of the right tools such as jacks, oil drain pans, gloves and more—to ensure the job goes smoothly. On top of that, Advance Auto Parts also recycles used motor oil.  So after you perform an oil change, bring your used oil back to the store for clean and easy recycling.