There’s a lot of contention in automotive circles about synthetic and conventional oils. While some hold that the older stuff is better, or at least better in older cars, the proponents of synthetic oil are adamant that it’s the good stuff.
It’s a rather complex subject, with a lot of different variables to account for. If you’re ready and willing to step into it then let’s get started on the essential differences.Different Chemistry
Oils are graded according to their Base Group, which are as follows:
- Group I oils are the cheapest on the market. They’re put through a simple solvent refining process and are classified as being oil which is less than 90% saturates and having a viscosity index(VI) of 80 to 120 while containing more than 0.03ppm sulfur.
- Group II oils are close to the same in price these days, and are put through a hydrocracking process, which is much more involved than solvent refining. They’re required to be more than 90% saturates and having a VI of between 80 and 120. They’re also required to be less than 0.03ppm sulfur.
- Group III oils are put through a more strenuous hydrocracking than the former group, and must be more than 90% saturates, less than 0.03ppm oil, and must have a VI greater than 120. These are often considered the lowest grade of “synthetic” oils.
- Group IV oils are created from polyalphaolefins(PAO) and are considered to be fully synthetic despite many sources of PAO being derived originally from petroleum based chemicals.
- Group V oils are considered to be any other base oil. Most often these are produced from esters, and they’re used as additives to other oils rather than being used strictly on their own.
For the most part, Group I and II oils are considered to be strictly mineral oils, while Group III sits in the middle although it is currently legally considered to be a synthetic oil as the components are changed sufficiently from Group II oils.
As a general rule, Group V oils are rarely used on their own, instead they are used as additives. Quite often they’re combined with Group IV oils to create a synthetic oil which has the best properties of both.
An oil labeled as “Full Synthetic” on the container is more of a marketing thing than any quantifiable measurement.
It’s important to remember that “synthetic” oils are still most often produced from the components of crude oil. However, they have been purified and separated from the base impurities of most mineral oils enough that there is a serious difference.
Real-World Performance
Synthetic oils take the lead here, and always will. There’s a few different reasons for this.
Oil isn’t a homogenous substance, instead it’s a complex mixture of hydrocarbons, waxes, and other components. Mineral oils have impurities due to the raw crude oil used to produce them and the quick processes used to create them.
Synthetic oils are also created from a wide array of hydrocarbons, but they lack many of the impurities which can be found in conventional oils. Instead, they’re created carefully and in a homogenous manner. This increase in purity lends a consistency to synthetic oils which simply isn’t present in mineral oils.
Most of the contaminants which can be found in conventional oils are eliminated in the process of creating a synthetic oil. Things like sulfur and nitrogen can create problems over time in even the hardiest of machines, leaving deposits in gaskets and seals and giving them a lesser lifespan when compared to their synthetic counterparts.
Another big factor is design.
Synthetic oils can be specially designed for specific purposes. This is where the blending of Group V with Group IV oils makes a major difference. When an oil is purposefully designed for a purpose, rather than simply thrown into the mix, it leads to a great difference in performance.
Compared to conventional oils, synthetic oils offer better performance in the following places:
- Operating at temperature extremes
- Lowering temperatures of the operating engines
- Longer lifespan when compared to conventional oils
- Resistance to oxidation, reducing sludge problems
- Extended lengths of time before needing replacement
- Decreased evaporative loss
- Higher VI
- Better lubrication in extreme cold weather
- Better “hot spot” protection
If maximum performance is what you’re looking for, then synthetic oils are going to win out literally every time. They’re more pure, purposefully designed, and perform better in the field than any comparable conventional oil.
Financial Costs
Anyone who’s looked to replace their engine oil knows that synthetic oil costs much more than conventional oils.
It’s simply a side-effect of the greater processing which goes into the creation of the oil. More processing and more time involved is always going to lead to a greater cost for the end consumer after all.
Most synthetic oils are destined to end up in automobiles and some people are split on which actually ends up being the less costly option due to the following factors:
- Often, synthetic oils will last at least twice as long as conventional oils and sometimes more. With the adaptation of modern oil sensors, they often have a surprisingly long life span.
- Money can be saved due to the increased viscosity of the oils which keeps fuel efficiency up.
- While the jury is still out, some people swear up and down that synthetic oils reduce wear and tear on an engine which can lengthen the life of an engine. Where true, this puts off costly repairs or replacement of an engine for quite some time.
Most of the common myths about synthetic oil, such as never being able to go back to conventional oil in the same motor, simply aren’t true. Although the people who sell it to you would certainly think it would be.
That said, with the much higher upfront costs of synthetics, conventional oil is still a more economical option for the average driver.
Environmental Impacts
While synthetic oil is quite often touted as being a lot greener… the jury is still out. There are some biologically derived synthetic oils which don’t require a petroleum base, but as a general rule most of the synthetic oils on the market are still derived in some fashion from crude oil and have a higher energy impact.
Any kind of oil can be recycled with the proper processing, whether conventional or synthetic, which is really where the focus should be.
That said, synthetic oils shine with a much longer lifespan than mineral oils. Less oil pulled, and proper recycling of the resulting waste oil, could theoretically reduce global oil demand by quite a bit if everyone were to switch to synthetics tomorrow.
They also have a tendency to evaporate at smaller quantities at high temperatures, which means less “topping off” of a system is needed and reduces the overall oil demand of a vehicle which is using synthetic oil.
Synthetic oil wins this round again, but not by a long shot in most of its current forms.
Oil By Design
If you own a newer vehicle, you may not have much of a choice, modern engines are often designed to be used only with synthetic oils. That means that you’re not left with much of a choice as an end consumer.
While a conventional oil of the same weight will work, in these cases you’ll experience worse fuel efficiency, lowered power due to higher initial drag, and more wear-and-tear on the motor.
However, most older engines will benefit quite a bit from synthetic oil. There’s one exception however: quite old engines may have leaks in gaskets and seals which are blocked by deposits left behind by conventional oil.
A good synthetic oil is going to break these deposits down, making problems that were already there readily apparent as soon as the purer oil begins breaking down these deposits. While older versions of ester oils could sometimes be hard on seals, the same isn’t true of modern formulations.
If in doubt, just consult the owner’s manual and follow the instructions there. Car manufacturers aren’t exactly “in cahoots” with oil manufacturers, although by now we should all know the old 3,000 mile rule isn’t true.
The Verdict: Synthetic Oil Is Better
The advantages offered by synthetic oil are impressive any way you look at it. In real world performance and environmental impact they’re simply better, but the higher cost can be somewhat of a turn-off for many consumers.
For the individual consumer, however, the financial costs may be a bit hard to swallow however. While certain synthetic oils may end up being cheaper in the long run, due to the lengthened life span.
So, in the end by all measures of performance and impact synthetic oils are better… if you can afford it in the first place.
Conventional oils have a lower upfront cost, but may end up costing more in the long run.
Both still have a place in the world, but as more and more manufacturers design engines to use synthetic oil, conventional oil may not have a place in the end consumer world for much longer.