A look at modern advances in vehicle oil formulation.
As engines and their lubricating oils have become more complex than ever, Rob Marshall explains why the “that’ll do” approach could be an expensive mistake.
An engine would not last long without oil. In the absence of lubricant to separate its various moving parts, they would rub together, overheat and seize. While engine oil continues its critical lubrication roles, by minimising friction and dispersing heat, the increasing sophistication of modern engines, which experience higher loads and extended drain intervals, mean that additional tasks must be fulfilled by the oil to preserve not only the engine but also hardware that is positioned outside the crankcase, from turbochargers to antipollution equipment.
The make-up
Perhaps understandably, the huge advances in oil chemistry tend to be unappreciated, even among many professional mechanics. Base oil represents around 75% of a typical engine oil’s volume, consisting of quality categories that are ranked from Groups 1-5, with the last of these being the highest class. Most engine lubricants use Group 3. An exception is Shell – its Helix Ultra branded engine oil range is produced through the corporation’s Gas to Liquid technology, from which man-made base oil is created from selected building-blocks of natural gas. The company claims that this contains virtually none of the impurities that exist in base oils derived from crude, as well as possessing stronger molecular bonds. Added to the base oil is a complex additive pack, representing the remaining 25% of volume. Developed by specialist chemists, often in collaboration with a car-maker, or engine designer, the process is immensely time- and cost-intensive – engine testing alone can cost well into six figures, with different powerplants being used to evaluate the formulations.
Viscosity Improvers (VIS – also called Viscosity Modifiers) maintain the oil’s ability to flow consistently across a wide temperature range. More VIS tend to be used in oils that display a wider viscosity difference between their ‘winter’ and ‘summer’ grades. For example, a 15W-40 oil is likely to contain a reduced quantity of VIS compared with a 5W-40. VIS pose a problem for petrol direct injection (GDI) engines particularly, because they attract deposits that stick to the cylinderhead inlet port walls, most of which originate from recirculated exhaust and blow-by gases. Eventually, a rubbery accumulation restricts the intake sufficiently to affect engine performance. Removing the exhaust gas recirculation (EGR) valve is illegal, so the solution is to blast crushed walnut shells under pressure into the inlet casting within the cylinderhead to dislodge the deposits without damaging the aluminium casting. Manufacturers of more recent models publish their own engine oil specifications, which are likely to include strict limits for inlet deposits in these GDI applications.
Within the crankcase, a detergent removes combustion deposits and a dispersant holds them in suspension. Both of these ingredients are responsible for fresh lubricant turning from a golden hue to dark brown/black in use. Should the incorrect specification oil be used, or the drain intervals be neglected, particles might build within the engine. Driving conditions play a role, too. Stop-start and low-speed conditions, especially those in which the engine oil does not achieve normal operating temperature of around 80-120°C, and driving in very dusty atmospheres, can promote higher levels of crankcase deposits.
Engine oil gets much hotter during continuous high-speed and load conditions, especially if the sump level falls below the recommended minimum. Because lengthy motorway runs can see engine oil exceed 100°C by a considerable margin, anti-oxidant additives help the lubricant to resist premature degrading and evaporation, which would raise oil consumption and reduce engine protection. The constituents left behind can form a damaging black sludge. As combustion gases tend to be acidic, corrosion inhibitors are included also within the additive pack. This is one reason why it’s a good idea to change the oil before the car is stored for any period of time, because the old oil’s corrosion
inhibitors would have been partially, or wholly, depleted. While additional friction modifiers and anti-wear additives are also employed, anti-foam components prevent issues with crankcase ventilation and potential pressure build, caused by foam forming on top of the oil.
New tech – new challenges
The current generation of small capacity, turbocharged petrol engines has been developed to meet the demands of both car-makers and legislators to reduce both fuel consumption and exhaust emissions. The irony is that industry experts have made it public that they will
be unable to meet next year’s Worldwide Harmonized Light-duty Vehicles Testing Procedure (WLTP), because the original laboratory figures were found to not be representative of real-world conditions. For more information, see http://
wltpfacts.eu. With Herbert Diss, CEO of Volkswagen, having announced last year that “…the trend of downsizing is over… (because) emissions tend to go up as engines get smaller”, it could be that these super-tuned ‘tiddlers’ have had their day and higher capacity engines in a milder state of tune are likely to be the future. For now, at least, the special lubrication needs of these engines must be considered, as the relevant cars are entering the used car market.
From a service point of view, extra-low viscosity lubricants (such as 0W-20) have been developed (most of which comply with the newest ACEA C5 specification) in cooperation with engine designers to reduce frictional losses that can be responsible for up to 20% of the energy released by the fuel being wasted. Shell told CM that the 0W range is the fastest-growing category in North West Europe. Because such small-capacity engines are also equipped with forced induction – typically turbocharging – the oil is not only placed under extra thermal stress but a new phenomenon has also arisen: detonation or Low Speed Pre-ignition (LSPI).
Thanks to these engines' design, which combine both cubic capacity downsizing with crankshaft down-speeding, LSPI has become a notable problem due to elevated pressures and higher temperatures encountered within the engine cylinders. The condition tends to be more prevalent under heavy acceleration at low engine speeds, when the fuel mixture explodes (usually as the engine piston is rising) rather than burning smoothly. While it is unclear whether, or not, this condition has been left until mass production for the problem can be addressed fully, work continues to mitigate the serious mechanical damage that results from uncontrolled detonation.
While LSPI has multiple origins, engineers have cited an interaction between the fuel/air mixture and the small quantity of engine oil that is present on the engine cylinder walls as a factor. As the engine piston rises, the conditions cause the minute quantity of oil present to ignite, resulting in the fuel/air mixture combusting at the wrong moment. Reports state that the complex ratios of additive ingredients, with specific focus on calcium carbonate in the detergent additive, are responsible. Obviously, retarding the ignition by controlling the spark timing alone cannot control this phenomenon. Dr Jochen Lach, engineer of engine oils at Shell Global Solutions, a corporation that works closely with Chrysler, BMW, Daimler and Hyundai at their engine development stages, advises that lubricant developments to address LSPI are ongoing, but he advises
CM readers who either buy oil or trust a garage to do the work for them, that they must ensure that the lubricant meets not just the viscosity but also the individual manufacturer specification provided in either the owner’s manual, or service book.
Obviously, if your engine suffers expensive piston or valve damage and the car is covered by a warranty, you will need to prove that you have been responsible and followed the manufacturer’s oil requirements.
More than just the engine
It is remarkable that turbochargers last for any length of time at all, considering that their rotors can reach speeds in excess of 200,000rpm, let alone being exposed to significant heat levels, particularly when employed in petrol engines. While using the incorrect oil might affect adversely the required protection levels of a turboshaft’s bearings, not changing the oil on time can cause particles to build on the strainers of either the oil pump and/or turbo oil feed line, which is a common complaint levelled at the FORD/PSA co-developed DV6 diesel engine. Usually, turbo failure is the first symptom of an underlying problem with the lubrication system and further investigations should follow. The majority of turbocharger suppliers, for example, will refute a warranty claim if it cannot be proved that the oil supply line has been replaced as well.
All vehicle engines consume oil to an extent, but any deposits that originate from the lubricant have their own ramifications for exhaust-mounted aftertreatment hardware. While the delicate honeycomb structure of precious metals within a catalytic converter can be damaged by lead deposits from leaded petrol – which, in part, hastened
its demise as a road fuel in the UK at the end of 1999 – engine oil blenders have had to alter their formulations to ‘catalyst friendly’ blends, including reducing ZDDP concentrations.
The introduction of diesel particulate filters (DPFS) in the early 2000s, which became mandatory with Euro V emissions legislation being introduced at the end of the decade, necessitated new low sulphur, phosphorous and sulphated ash (SAPS) engine oil formulations, underscoring the ACEA C specifications. Not using a LOW-SAPS lubricant in a Dpf-equipped vehicle won’t cause an instant blockage, but the problem will manifest itself over time. Naturally, the DPF itself gets the blame, when the real cause was incorrect oil. Thus, buying a Dpf-equipped vehicle can be risky if you do not have evidence that the correct oil specification has been used throughout its life.
Gasoline particulate filters (GPFS) entered production this year to address the higher soot levels produced by GDI designs – in most cases, they require the same low SAPS oil as required by DPFS, but check your handbook carefully.
Choosing the right engine oil
When choosing oil for classic cars especially, you need to compare the API/ ACEA specifications, as mentioned earlier. In the case of 10W-40 and 15W-40 viscosities, in particular, you may find diesel-only choices; these tend to contain higher detergent levels within their additive packs, to deal with the combustion characteristics of the fuel. Both mineral and semi-synthetic blends might be available as well and the latter might boast superior performance under high temperature conditions, making semi-synthetic a better choice for turbocharged applications.
The days of a universal modern engine oil, defined solely by its Society of Automotive Engineers (SAE) viscosity grades, are long gone. Many engines from 2000 onwards have manufacturer-specific requirements, making choosing the right oil considerably more complicated and ever more important. If you find several different oils that claim to meet your car-maker’s specification, should you choose the most expensive?
Like many multi-million-pound industries, major oil companies and blenders spend considerable sums on promoting their brands. Shell, for example, has one of the longest and most successful motorsport partnerships with Scuderia Ferrari, as well as partnering Hyundai at the World Rally Championship and the
FIA World Endurance Championship, and sponsoring BMW’S DTM (German touring cars) exploits. In such cases, the customer ends up footing the bill and sceptical value-oriented motorists may view such extravagant activities by large multinationals as vanity exercises that have no relevance to the oil they put in their car. We put this to Shell, whose spokesperson explained that its involvement in motorsport allows its engineers to identify the limits of what is possible; in the real world, this can result in consumer lubricants that exceed manufacturer specifications. For example, the company cites up to 32% superior resistance to oil degradation compared to the API SN specification.
However, unlike Shell, SCT Lubricants (which sells its lubricants under the Mannol brand in the UK) undertakes neither R&D programmes with carmakers, nor expensive sponsorship activities. Jevgenij Lyzko, MD of Mannol UK, explains that his brands can be trusted to deliver on the quality statements printed on the packaging: “Like creating a cake, we know the recipe that results in the oil meeting a certain specification. We buy the required ingredients from carefullyselected additive suppliers that work directly with the car-makers. This is why our brand can comply with stipulated manufacturer specifications. Yet, because we undertake no motorsport, or R&D programmes, we pass the cost savings to the customer.”
Who can you trust?
Just as the counterfeiters have brought us inferior quality car parts, engine oil is also a target for unscrupulous traders. Until their premises were raided in 2016, a pair of Russian ‘entrepreneurs’ were quoted as making €146 million a year making and selling low-quality oil in counterfeit packaging. They are not the only ones. Shell told us that its anti-forgery solutions include product tracking and authentication technology, and it works with local authorities to prevent and reduce the manufacturing and distribution of counterfeit Helix Ultra products.
While not illegal, some engine oils from respected brands lack any ACEA/ API claims. Comma, for example, retails three 20W-50 viscosity oils, one of which does not bear any independent specification claims on its packaging. When CM asked the company’s technical division, we were told that while the oil does not claim to meet any standards, it provides ‘basic protection’, although no further elaboration was provided. ACE Nosmokeoil claims that its three oil ranges (20W-50, 10W-40 and 5W-30 viscosities) offer a “universal solution” and “works in all major motor manufacturer’s engines, both petrol and diesel… covering all vehicles.” As there are no ACEA/API specifications printed on the packaging, especially as no low SAPS details are specified (therefore making the oil likely to encourage DPF blocking), we asked the UK supplier to which specifications