Before reading this article it is worthwhile for you to read my article about Base Fluid Types. Knowing the basics beforehand will help you understand this article more easily.
I often see or hear the statement about how “full synthetic” oils are not really synthetic and they are actually highly refined group III (Grp III) petroleum oils instead. While it is certainly common these days for “full synthetic” oils to be made using Grp III base oils, it is not always the case. There are brands making full synthetic products utilizing group IV (PAO) base oils as implied by the “full synthetic” moniker still. I refer to these products as “true synthetics”.
Group V (ester) base fluids are another type of synthetic but they are uniquely different from both Grp III and PAO oils. Grp III and PAO are extremely similar in how they are utilized in lubricating oils. They can often be directly substituted for one another without major formulation concerns. So the comparison of those two is where I am focusing this article. Most synthetic oils use some amount of esters in them regardless of whether they use Grp III or PAO as the main base oil, but I’m not going to go in too much depth about esters in this article.
The big difference that most people focus on is the price and rightly so. True synthetics are just plain expensive. No matter which company makes it or how it’s made, PAO and ester base fluids can be 1.5 to 4 times more costly than Grp III oils. True synthetics just cannot compete on price with Grp III oils and even with the economies of scale, that can’t be helped.
As refining technology has improved, Grp III oils are now extremely close to PAO oils in many performance categories. However, Grp III base oils can only approach the performance of PAO base oils so much because refining processes can only change the molecules so much. Since no process is perfect, there will always be some unstable molecules in the refined oils. This instability is mostly caused by unsaturated bonds in the molecules, which are openings for oxidation to occur. PAO synthetic molecules have fully saturated molecules making them less prone to oxidation.
Although viscosity modifiers contribute heavily to low and high temperature viscosity performance, the natural viscometric stability of PAO is better than Grp III. So after being used for several hundred miles, the polymers may be sheared to a point that the natural viscosity characteristics of the base oil have a big effect on performance. When that is the case, PAO has an advantage over Grp III.
There are two performance advantages that typical Grp III has over PAO that are not widely known. The first is most additives have better solubility in petroleum oils like Grp III so they mix more easily than they do in PAO. That is one reason why esters are so commonly used in synthetic formulations because the ester base fluids increase the overall additive compatibility. So it is rarely an issue in either type of oil, but the Grp III does have a better natural ability to keep additives from separating.
The second advantage Grp III has is its sludge handling properties and it is a bit more complicated than the additive compatibility issue. Sludge is produced as an oxidation byproduct. So Grp III actually produces more sludge than PAO does. However, Grp III keeps that sludge from separating for the same reasons it keeps additives from separating. This dissolved sludge increases the viscosity of the oil but resists separating. PAO, on the other hand, does not dissolve sludge as easily. So even though PAO produces less sludge through oxidation, the sludge that does form has a higher tendency to separate from the oil. Similar to the additive solution, ester base fluids blended with the PAO can stop this from happening, but still, Grp III* has the natural advantage in this property.
*As a matter of fact, it is actually the “impurities” of the Grp III base oil that help in this regard, so the less refined an oil is, the better this ability can be. A Group I or a Group II oil could actually outperform a Group III if the antioxidant performance is high enough.
One additional difference that true synthetics have compared to Grp III is the drain interval. Most PAO based full synthetics tout extended drain intervals that make the upfront cost more reasonable. By the time the extended interval has elapsed, it can be double the mileage in some cases; and having to buy oil (and do oil changes) half as often is a valuable consideration for many people.
Which One to Choose
On one hand, “close enough” is good enough for many riders, and taking that stance is unlikely to result in any problems for most people. The performance benefits of true synthetics are there, but most real world motorcycle applications rarely stress the oil enough to fully realize those benefits. Racing applications or extreme environments, like snow riding, mudders, or desert riding, will push the oil to its limits, but the average riding situation won’t be brutal enough to necessitate a true synthetic.
On the other hand, some people just want the “real thing” and want to get what they pay for, which I can absolutely relate to. Since Grp III is much cheaper than PAO, that cost difference should show in the retail price. So if I were buying a Grp III oil, I would expect the price to be much less than a comparable true synthetic product.
Some people simply want the very best product they can get; even if the benefits of it are hard to see or quantify. Peace of mind can be a powerful thing, and the peace of mind that comes from knowing you are using the best possible type of product can make it worth the added cost. A more tangible possibility is that the performance benefits of true synthetics may be the difference between an ugly failure and business as usual in a critical situation.
Is a failure like that probable? No, but that isn’t to say it doesn’t happen.
I’ve heard enough stories from customers and other riders about bikes running on the ragged edge, which kept going long enough to get into the shop before catastrophe struck to convince me that it does happen. So those extreme circumstance mentioned above (racing, desert riding, mudders, and snow riding) can definitely warrant the use of a true synthetic and sometimes a worn machine that is over-stressed can push the oil to its limits.
It would be impossible to truly attribute the differences between Grp III and PAO base oil as the cause or demise of an engine in the case of a failure, but I would be surprised if it hasn’t been the case in more than a few engine failures and near misses.
How to Tell the Difference:
So how do you tell if a company uses “true” or Grp III synthetic base oils to make their product? One way is looking up the safety data sheet (SDS) for the product. SDS’s can be a bit cryptic and some companies just don’t include as much information in theirs as other do, but often you can gain some information from them. There are two areas of an SDS that can give you some clues, sections 3 and 15. Section 3 of most SDS’s is the composition section and section 15 is the regulatory section. Section 3 will often give you a clue as to the type of base oils are being used. If section 3 is too unclear, section 15 may have additional information.
Here is a list of the commonly used words for the different types of base fluids in SDS documents:
- Mineral oil
- Petroleum oils
- Petroleum distillates
- Severely refined
- Solvent refined
Ambiguous (Maybe PAO or ester but possibly Grp III):
- Synthetic oils
A good thing about most true synthetic base oils is that they are not often considered hazardous. That is great for our health and the environment, but it also means they are typically excluded from SDS’s since the document is meant to illustrate potential hazards. So they are not always listed on the SDS. However, petroleum base oils are rarely excluded so the lack of any base oils on the list tends to point to at least some true synthetic content.
SDS’s can usually be found on either the manufacturer’s website or through a quick internet search using the name of the product and either “SDS” or “MSDS” (~product name here~ sds or ~product name here~ msds)
There is another way to find out information about the composition of the products you are buying. This method should result in you knowing exactly what you are buying and answer all of your questions. Call the manufacturer! Call the technical service department for the brand you are curious about and ask them direct questions. Some companies may be guarded with their information and be reluctant to tell you anything, but I’d bet a fair share of them will be very forthright and answer your questions. The trick is to ask questions with yes or no answers or questions that require very direct answers. Questions like:
- Do your full synthetic products use group III base oils?
- Do your full synthetic products use Group IV or Group V (PAO or ester) base fluids?
- What types of base fluids are used in your synthetic products?
If the responses you get don’t really answer your questions and you have people telling you about “synthetic performance” rather than synthetic content, you can be pretty sure that they are not using true synthetic base oils. Regardless, you will have learned something about the products and gained some knowledge, so it is worth the phone call either way.
So Does it Really Matter?
Grp III base oils have extremely good performance and really do compare well against PAO in a lot of performance categories. They are much more stable than their group I and II counterparts in the range of petroleum oils. They lubricate well and are very versatile for formulators to use due to better additive compatibility and lower costs compared to PAO. The performance benefits of PAO over Grp III mentioned earlier in the article are real and quantifiable in lab tests. However in a real world situation such as a motorcycle engine, those benefits are much harder to quantify and likely imperceptible to most riders.
If you were hoping to have a clear and definitive answer by the end of this article, I’m sorry to disappoint you. From a technical standpoint a true synthetic is the better option. From a consumer standpoint, the added cost of true synthetics might not be worth it for the average rider. For racers and people riding in extreme conditions, I think true synthetics are the way to go. In the end, the only person who can decide what is right for you, is you; but I hope now you can make that decision with a better understanding of what you are really deciding between.