Should You Use Synthetic Oil in Your Vehicle?

Should You Use Synthetic Oil in Your Vehicle?

Last week we explained the basics of motor oil, from viscosity to additives and everything in between. Now it’s time to tackle a much more contentious issue: synthetic versus conventional. Which lubricant should you use in your vehicle? Is the extra protection afforded by man-made oil worth the added expense?

Synthetic Versus Conventional

Oil-Platform-01.jpgTo understand the benefits of synthetic oil you first have to learn how it differs from dinosaur juice. Conventional lubricants are made from crude oil. It’s extracted from the ground and then extensively refined to remove impurities. After that it gets blended with other chemicals before landing on the shelf of your local auto-parts store. But according to Jared Martin, National Automotive Retail Accounts Manager for Royal Purple Ltd., no matter what you do, “conventional oils have a level of insolubles – paraffin, waxes, silicon, dirt – natural contaminants.” Under certain conditions these substances can form deposits inside an engine.

By comparison, synthetic oils are typically manmade, though not necessarily, a point addressed later in this article. Martin said “[they] are usually derived from natural gas or alcohol,” meaning they’re pure from the get-go, containing no undesirable contaminants. They’re also more stable at a variety of temperatures. They don’t thin out as much when they get hot or excessively thicken in cold weather.

Royal-Purple-Oils-01.jpgZ. George Zhang, PhD and CLS manager of Valvoline’s R&D Lab in Lexington, Kentucky said, “the better oil, like a synthetic oil, the VI (viscosity index) will be higher – [meaning] the viscosity changes less with temperature, which is a desirable trait.”

Further complicating things, many refiners offer synthetic blends. These oils are generally less expensive than pure-bred synthetics, but they also offer less protection. As always, you get what you pay for.

Synthetic Advantages

Another major benefit of synthetic oil is molecular consistency. Being an impure substance, conventional lubricants are made up of molecules that are all different lengths. According to Zhang, there are small, medium and long hydrocarbon chains. Synthetic oil is comprised of only medium-length molecules.

The problem with conventional oil is that those short, lightweight hydrocarbons tend to burn off when they get hot. This causes the oil to thicken the longer it’s in an engine.


Aside from that, synthetic oils also handle high temperatures better than conventional lubricants. They’re better at transferring heat, meaning synthetic oils can actually help a vehicle’s engine run cooler.

Being more resistant to breakdown or “shearing,” synthetics are much more robust than conventional lubricants, something that can really pay off. According to Martin the drain interval can safely be extended anywhere from 10,000 to 12,000 miles, or three to four times normal oil, while the added cost of synthetic is nowhere close to that.

Some niche oil companies advocate even longer drain intervals, up to 25,000 miles, but this is quite extreme and not something Zhang recommends.


Pistons-Motor-Oil-01.jpgYet another way synthetic oil can save drivers money is through improved fuel economy. Don’t go looking for a huge increase if you make the switch, but Martin said Royal Purple can actually boost efficiency by around 2 to 3 percent, a modest but welcome improvement.

Of course there are other ways to save money at the pump. Pete Misangyi, Supervisor of Fuels and Lubricants at Ford said they’ve switched to lighter weight 5W-20 oils in order to trim fuel consumption. These oils are easier to pump, meaning less energy is wasted.

Ford has also started to use variable-displacement oil pumps, which move less oil at lower engine speeds to help boost efficiency even further. With these improvements, Ford has started advocating 10,000-mile change intervals on its vehicles, helping lower maintenance costs for customers.

Magic Ingredients

Petroleum-based lubricants have many disadvantages compared to their synthetic counterparts, but there’s more to oil than oil. “We’re not just relying on the synthetic base stocks for the benefits of Royal Purple” Martin said. “[It’s] really just a carrier for the additives” he said, noting “I would take a well-formulated mineral oil over a poorly formulated synthetic oil.”

Downsides: Dispelling Rumors

Of course the benefits of synthetic come at a price. They’re usually several times more expensive than old-fashioned lubricants. But with longer drain intervals and improved fuel economy “the benefits of synthetic justify the expense,” Martin said.

E46-BMW-M3-S54-Engine-01.jpgMany of the other down-sides about synthetic oil simply aren’t true, including the notion that you can’t switch to it if a vehicle has been on conventional oil for a long time, as well as the idea that it should be avoided in older, high-mileage cars.

Zhang said decades ago synthetic-oil makers didn’t pay attention to seal compatibility, which caused seals and gaskets to harden or get brittle, leading to leaks and other issues. This is where these myths about synthetic oil likely originated. But he points out that was 20 years ago or more and “that’s not an issue anymore.”  Misangyi seconds this. He said “a proper [oil] blend shouldn’t have any issues.”

Group III versus Group IV: When Synthetic Isn’t

As mentioned earlier, not all synthetics are created equal. As you’d expect, many are formulated in laboratories, but unbelievably some are actually made from crude oil! How can they be labeled as “synthetic” if they’re made from petroleum?

Engine oils are classified into five different groups. For this explanation we’re focusing on Group III and Group IV lubricants. Group III oil is a very highly refined conventional product. Group IV lubes are made from synthetic sources, oftentimes natural gas. They’re also known as PAO base stocks, which is short for polyalphaolefin. Don’t worry; you won’t be tested on this.

From a performance standpoint Group III and Group IV oils are essentially identical, so don’t lose any sleep over this distinction. Zhang said under scientific analysis he has a hard time telling them apart.

Other Oil Myths

On the subject of engine oil there are several other common myths worth noting. One of them has to do with break-in lubricants.

A lot of people seem to think automakers fill engines with special oil from the factory that’s designed to help them break in quickly. According to Misangyi this is “generally a myth.”

2011-Ford-Mustang-V6-Engine-01.jpgAdditionally, some drivers think they need to change a new vehicle’s oil more frequently than recommended in order to flush out potentially damaging metallic particles that are formed during the break-in process. According to Misangyi there is no need to do this. He said there’s been “a five-fold reduction in engine wear metals in the last 30 years,” no doubt thanks to more precise manufacturing techniques and better lubricants.

Additives are another hot oil topic. Companies sell all kinds of supplements but Zhang says caveat emptor – buyer beware. He doesn’t recommend them, noting “you’re not getting the benefits [they claim].” It’s best to steer clear of these products and instead use quality oil and change it at a reasonable interval.

Which is Right for You?

Valvoline-SYN-Power-Oil-01.jpgIt’s probably hard to buy a bad lubricant these days. Even the most basic conventional oils available on the market are far better than ones offered just a few decades ago.

According to Zhang, it’s ok to use a quality petroleum-based oil in the average car, but with high-performance vehicles he recommends synthetic. Ultimately he said “follow the OEM’s recommendations.”

For Martin, “the benefits of synthetic justify the expense,” with longer drain intervals, reduced deposit formation and slightly better fuel economy. Misangyi also favors synthetics. Some of the benefits he cited include “longer engine oil life [and] reduced deposits,” thought he also recommends following what’s in the owner’s guide.

GALLERY: Should You Use Synthetic Oil in Your Car?


  • augie

    really enjoy these basic car maintenance/under the hood articles.  many times, enthusiast articles/reviews assume a basic level of knowledge that i don’t have!  other ideas might include types of differentials (including electronic), types of suspensions, etc.  keep up the great work.

  • Wursters3180

    Wurster”s Foreign Car Repair recommends to have your oil changed every 5,000 miles. We don’t recommend 10,000 – 12,000 mile oil change because it has been proven that the oil becomes sludge and causes major problems. Call us and we can go into more detail. (615)790-3180

  • Arthur H. Neill, Jr.

    In my (2) 1989 Cadillac Fleetwood (FWD) automobiles, I change the oil every 7,500 miles.  Owners will find this interval recommended in GM users manuals dating back to the 1950’s.  I’ve had  only one oil pump failure since I owned my first car in 1967 and that occurred at 150K miles in one of my two Fleetwoods.  I have always used the multi-viscosity oil recommended by the manufacturer . Changing the oil more frequently might be necessary if you drive a cab in the  city or in Death Valley but for routine driving using non synthetic oils, an oil replacement interval of 7500 miles has served me well.

  • dana king

    Change your oil and synthetic brings nothing to the table except high profit for the retailer!

  • cvcc

    I guess you dont understand what thermal transfer along with viscosity and shear stability mean.

  • dana king

    I understand totally. I build $100,000.00 race motors. You build arguments which sells profits?

  • Doug

    Which is better synthetic engine oil after 5000 miles of use or fresh non synthetic oil?



  • Sgt schultz

    Some engines are just meant to run … The term is MINERAL oil, not ‘non synthetic oil’

  • Moliu

    NEVER use synthetic oil before, ,just regular 5W30 ” cheap Penzoil mostly” in all my Toyotas (04 corolla/06 matrix/2000 4 runner)-all 3 mileage have past 500K +km.. Just regular oil change every 8K km, tune up(basic spark plug change, etc) every 160k km. at my regular mechanics, Not at Toyota dealers. Never had any performance issues, all still running like new. I am in Canada, temperature span from summer 30+C to -25C winter. (5W30) recommended by Toyota. I don’t use a block heater and my cars are not garaged. Cars starts with no issue on the coldest day. My cars deliver newspaper/magazine on a daily basis from Toronto to Montreal, that’s why the high mileage. Lots of highway and city driving in Montreal city centre. (the crazy Montreal/Laval traffic jam, and traffic lights stop and go-no problem at all for my toyota engines).. lol

  • Rose

    Do I have to change the synthetic oil in my 2008 diesel engine motor home in the spring after it has sat through the winter. It has been started every 2 weeks and let run from 30 min to an hour. It has been driven only 2000 KM last summer

  • Mentallect

    Group III is not synthetic oil. Synthetic by definition means polyalphaolefin. I ran Mobil One, 0W-40 Euro synthetic in my Camry with 13,000 to 16,000 oil change intervals. Over 250,000 miles now, quiet as a mouse, 35 mpg on hwy, no leaks, and you can’t do that with a Group III synthetic oil.

  • Mentallect

    No he doesn’t. Synthetic oil is Group IV or V, superior at the molecular level. Intelligence is good.

  • Jim Kener

    173,000 miles and still going, no engine problems, smog check shows car runs like new used a conventional oil for 16 years and changed oil every 7,500 miles as manual stated to do.
    Is a synthetic oil better probably but do you need it probably not unless you have a specific need. In prior cars I used Castrol only in the one with 173,000 I used major brands like used at a Quiky lube, Firestone and Chevron oil change service all engines did great.

  • Arthru

    Which is better non synthetic engine oil after 5000 miles of use or fresh synthetic oil?

  • Outcast_Searcher

    The article and every decent mechanic I’ve talked to says oil in vehicles should be changed at least once a year, regardless of the mileage. Breakdown of the additives is the most cited reason.

    Is it worth it to risk ruining your motor over an oil change once a year? That sounds penny-wise and pound foolish to me.

  • Outcast_Searcher

    If this was in the same car, it could be an engine problem and not the oil.

    I saw this kind of thing mentioned in a couple articles a while back. You should keep an eye on your oil level regularly, and check with a competent mechanic.

    Running with very low oil can be disaster for an engine.

  • Outcast_Searcher

    It depends on lots of things. If you have a “normal” car that you don’t drive hard and you change the oil frequently and you don’t expect to get over 200,000 miles on the engine, then the extra cost of synthetic oil might not be justified.

    However, if you do drive the car hard, have a high performance engine, or want the engine to last well over 200,000 miles, then synthetic oil can help your engine last.

  • Outcast_Searcher

    It depends on the car, how it is driven, on the oil used, etc. Lots of factors. Acting like one answer fits all is probably inaccurate and may be deceptive.

  • Outcast_Searcher

    Using the right viscosity, including multi-viscosity oil in cold climates, as recommended, is key. 7500 miles won’t do the trick for people who drive under 4000 miles a year. Even with synthetics, a minimal frequency of once a year is always recommended from what I’ve seen,

    But yes, generally, for a normal car driven normally, using the recommended oil and changing it frequently, the engine will last.

    One issue is how you drive. Short trips in cold weather, for example, is hard on oil. If in doubt, you should use the severe service interval.

  • Timmer

    My mechanic said that if you start using a synthetic or synthetic blend for more than two oil changes, you should not go back to mineral based oil….Any comment about this

  • Cory Hines

    Oil, like any substance in a sealed environment (like your engine), just isn’t going to go from full to low without some sort of other issue. Engine problem or a leaky oil pan, drain plug, or filter is more common. My guess, if none of these are a problem, someone changed the oil and filter, didn’t fill the filter with oil first when changing it, and when it circulated to the dry filter, you lost some oil to the filter.

    If you have an oil filter that mounts vertically, it’s best to lubricate the gasket and fill the filter with oil first before threading it on. This will cut down on loss of oil to the filter. However, if you can’t fill the filter before installing it without making a mess, simply lubricate the gasket and install it. In either case, once you fill the oil to the “Full” mark on the dipstick, make sure everything is tightened up, turn the vehicle on and let run for a couple minutes, checking for leaks. Once you determine there are no leaks to address, turn off the vehicle and check the dipstick again after the oil has time to drain back into the pan (couple minutes). If you were able to fill the filter first, you likely won’t have to add much oil if at all. If the filter was dry before starting, you likely will need to add more.

  • Cory Hines

    Your mechanic is misinformed. There is absolutely no reason you can’t go back to a conventional motor oil. The question is why would you want to?

    As posted in earlier responses below, it’s about changing your oil more frequently if you are running a lesser quality oil to keep contaminants and sludge from ruining your engine.

    If you decide to bounce back and forth from synthetic to conventional, just understand your intervals for changing oil and filters are going to fluctuate based on your driving conditions and what type of oil you are running. Don’t see you saving any time or money in the long-term switching between the two, but it doesn’t mean you can’t. Just ensure you are ALWAYS changing your filter any time you change your oil

  • Scott Ramaly

    I have switched from Dino to synth, and have found it causes leaks. I can smell burning oil when I shit off and get out of the car. I switched back to Dino and this doesn’t happen. I will stay with Dino as I do 3k Oci on my Versa.

  • Part Time Teacher

    I had a new 1978 Saab and put in an early version of Mobil One at about 30K miles. Went on a 600 mile trip. After about 150 miles, the oil light came on. Added a quart of regular oil (only thing available at the service area). By the end of the trip, I had replaced all 4 quarts, one at a time, with regular oil. On the way back, NO oil was used. So the synthetic did cause the leaks. However, I regularly used a newer version of Mobil One in a 1989 Saab with no problems. Whether it was the different formulation or different engine, I do not know.