Why synthetic oils are going to play such an important role in extending the life span of the internal combustion engine

A technical training video on this topic, presented by Automate Technical Trainer, Clint Flower, is available from Automate

Though it may have gone unnoticed by the vast majority of the buying public, last week marked a momentous turning point in the history of the automobile.
With relatively little fanfare, the world’s oldest automotive manufacturer – Mercedes-Benz – unveiled a car that seems to set the industry further along a radical and definite new path.
The car in question? Mercedes’ first ever production electric vehicle, the EQ C: a battery-powered, mid-sized SUV designed to undercut Tesla and spearhead the launch of a whole range of full-EV models from Benz over the next few years.
In short, the EQ C is a sign of the significant momentum building behind the mainstream electrification of automobiles, as more established players also signal their ambitious plans to enter the still-nascent EV space, and battery technology – crucially – matures to a point of critical price inflexion.
As an opportunity to re-shape the future of transport into a cleaner, more efficient mould, the EV surge is an exciting one; but it also represents a challenge for OEM manufacturers who still rely so strongly on the sale of internal-combustion-engined vehicles to keep their businesses running.
For these OEMs, then, the focus of the next few years will be managing the balancing act, and a big part of this will be getting their internal combustion engines as strictly-efficient and clean as possible.
With diesel on the nose in Europe and emissions laws tightening considerably across the US, Asia and the EU, there is a massive and renewed need to extend the life-span of combustion engines via new technology designed to increase the operating efficiency of ICEs.
The net result of this equation is that today’s already-complex IC engines are only going to become intricate and technology-rich, which has implications for how these engines are protected, lubricated, maintained and serviced.
Yes, even as the post-petrol era begins to dawn in the auto sector, for the time being at least engine oil will remain a crucial centrepiece of how our vehicles operate. In fact, in a world where efficiency becomes the yardstick by which all ICEs are judged, the design and quality of engine oil will be more crucial than ever.
We know that one of the most important factors in oil design is whether it’s mineral or synthetic-based. As more mainstream vehicles are fitted with complex fuel-saving systems like turbocharging, common-rail injection, cylinder deactivation, direct-injection and start-stop, and run increasingly-high compression ratios, the difference between mineral and synthetic engine oils will become more marked.
An important job for every technician is therefore to appreciate where engine technology is headed, as well as to clarify some of the important benefits of choosing a synthetic versus a mineral oil when it comes to modern, high-tech engines.
At the heart of the synthetic advantage is the ability to withstand oxidation – the physical and chemical deterioration of the oil – for longer, providing superior protection to intricate engine parts over the recommended drain interval. This derives, essentially, from the superior molecular structure in synthetic oil, combined with a necessarily lower percentage of additives and fewer general impurities in the finished product.
What makes the molecular structure of a synthetic oil so superior is the fact that the molecules themselves are far more uniform in shape and size than those found in a conventional base or mineral oil. These small, evenly-sized and shaped molecules help create a lubricant that produces less friction and an equal load share, particularly in areas of the engine subject to intense pressure, such as between the crankshaft and the conrod, or inside the bearing of a fast-spinning turbocharger.

Actually, the term ‘frictional load balancing’ is an important one to pause on. It refers to a positive characteristic in synthetic oil design that reduces permanent shear: the physical breakdown and destruction of modules which can decrease oil viscosity under normal operating conditions. The best way to understand ‘frictional load balancing’ is to think of ball bearings.
In conventional mineral oils, the oil molecules are like a collection of different size, oddly-shaped balls. In that situation, the larger balls cop more of the ‘load’ and stress, and their odd shape makes it harder for them to roll. Over time, and particularly in modern engines with their high-operating temperatures and tighter tolerances, these larger balls break and force higher loads onto their counterparts, to the point where eventually the shear damage becomes too great, and metal-on-metal contact occurs.
Now compare this to the synthetic molecular structure. In this case, the balls are equally-sized and equally-shaped, spreading the load evenly and, ergo, the wear too. This is a major advantage for synthetic oil users: it means the lubricant will have a very similar viscosity and performance rating at the end of its service interval as compared to when it was poured straight from the can into the car. If one performs a low temperature flow test, as pictured, it’s abundantly clear that while the grade and viscosity of the mineral oil has changed from new, the synthetic remains the same – even after 15,000km of wear and tear.
Given how sensitive modern, high-efficiency engines are to correct oil grade, particularly those fitted with DI and turbochargers, which generally experience much higher oil temperatures, the ability to maintain flow and purity characteristics for longer is a major advantage even for mainstream vehicle owners.
What’s particularly important to note is that these advantages are only increased when considering vehicles of increasing complexity, as well as those operating under more extreme driving conditions. High performance engines – which going forward will be forced to shrink in size while offering higher and higher levels of power – in particular demand extra wear protection to ensure they remain as efficient as can be. Synthetic oils with increased zinc additives are going to be crucial if these engines are to last as long as their forebears.
Then there’s the unique issue of hybrid engines. With battery range increasing, tomorrow’s hybrid vehicles are likely to spend more time with their engine off, restarting it only to charge the battery or to boost performance at higher-speeds. In this case, engine oil temperatures will not remain constant during a journey, meaning it will be vital for these cars to be running synthetic oils that offer outstanding cold start protection.

And it’s not just petrols and hybrids. Diesel engines, which are increasingly fitted with emissions control systems such as particulate filters, are forcing oil manufacturers to change the way they think about synthetic oils. Particulate filters, for example, are rather sensitive to sulphated ash deposits. NOx filters can be problematic too, and advanced catalytic convertors are susceptible to phosphor and Sulphur poisoning from inappropriate lubricants. Synthetic oils, designed specifically for these diesel engines, help overcome these issues, and offer additional protection for the turbochargers that are so crucial to a diesel engine’s performance characteristics.
There’s no doubt that motor oil has been the lifeblood of an automotive revolution that has driven us to the point where mobility and performance are taken very much for granted. But as the best engineering minds busy themselves with technical advancements that reduce emissions and improve engine efficiency, it’s critical that we understand which lubricants will best meet the demands of these increasingly sophisticated systems.
Already, the world of lubrication is a more complex one – a decade ago, a workshop could confidently service its customer vehicles with a 10W-40 oil for petrol engines, and a 15W-40 for diesels. Not anymore. Today, a typical workshop servicing three manufacturers might carry up to six different oil grades. Thanks to far more sensitive technical systems that find a home in even the cheapest cars, manufacturers have no choice but to mandate engine oil specifications that are stricter than ever before.
So yes, it’s clear that tomorrow’s cars are going to be more sensitive about the oil we lubricate them with. But what must also be remembered is that the benefits of matching the right oil to the right car will also increase as a result – and in that context, understanding the advantages of synthetic lubricants will be critically important for every one of tomorrow’s technicians.
Written by Harrison Boudakin for AutoMate Training, an industry leading provider of online, on-demand digital training.

Visit for a free 14-day trial.