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Avoiding a crisis: selecting the correct oil

By autotech-nath on September 19, 2020

Choice is not necessarily a good thing, especially when it causes confusion. Rob Marshall looks into the complex issue of selecting the correct engine lubricant, while providing updates on specifications that occurred earlier this year, while our attentions were diverted.

Not using the correct engine lubricant can have catastrophic consequences, for which you can be liable. The problem is that the later the engine, the fussier its lubrication needs, meaning that the ‘that’ll do’ approach must be an attitude that any technician must consign to the scrap bin.

According to Castrol’s Expert Technologist at its Pangbourne Research Centre, thinner engine oils can help reduce friction and boost fuel economy but, as the lubricant becomes ever thinner, there is an increased danger of metal-to-metal contact. This situation dictates that oil additives are ever more precision formulated to protect not only the engine but also emissions hardware. Proven by today’s lowest specifications not even existing five years ago, the rate of change in the engine lube field is accelerating and it is not easy for aftermarket technicians to keep up-to-date with the latest developments.

An overall trend has seen engine oil move from being defined solely by its viscosity to API (American Petroleum Institute) and/or ACEA (European Automobile Manufacturers’ Association) specifications and, now, manufacturer-set standards. Perhaps the most obvious consequence noticed by garages is the explosion of different 5W-30 varieties. In most cases, this is because the API/ACEA standards have become the base-line, to which manufacturers add their engine-specific requirements. While this has proven challenging for certain workshops’ stock levels, producing a ‘one-size-fits-all’ oil might be possible technically but is economically unviable. The result has seen some oil blenders, including companies that work with the OEMs, consolidate their ranges to help workshops. Total Lubrifiants (the company that sells Total Lubricants) told us that it covers the majority of the UK’s vehicle parc with five or six oil grades. Another OEM suppler, Castrol, highlights its range of ‘combi-products’, which also combine many of the key industry and OEM specifications. It advises that garages can contact the Castrol Workshop Team with specific queries if they are unsure.


While no formal blame has been directed at either engine manufacturers, or their lubrication partners, for not addressing these issues in the pre production stages, GDI engines suffer from particular ailments. These include LSPI (Low-Speed Pre Ignition) and timing chain wear. To temporarily address these issues, the API introduced its ‘SN Plus’ classification in May 2018, as an update to the pre-existing ‘SN’ specification to give the organisation sufficient time to develop a better solution. API SP was the result, introduced formally in May 2020.

Aside from the correct lubricant, ensure that you replenish the sump with the correct quantity. Consider that, on many diesel engines with particulate filters, some space is required in the sump for diesel fuel contamination that is a consequence of the active regeneration process.

Yet, API standards are not intended for the European and British markets. That role falls to the ACEA, which has not been as reactive. We contacted the ACEA about why it has not developed a Euro standard yet, equivalent to API SP, but did not receive an explanation before going to press. Therefore, when confronted with a modern GDI engine, technicians must select a lubricant that complies with the OEM recommendations.

Alternatively, you might notice oil recommendations from the International Lubricant Specification Advisory Committee (ILSAC) for latest engines, especially hybrids. ILSAC GF-6A is backward-compatible and boasts superior performance over API SN Plus. ILSAC GF-6B relates to 0W-16 oils only. Both specifications are for the latest engines, which focus mainly on extra protection for timing chains and LSPI avoidance.


The Verification of Lubricant Specifications (VLS) advises that checking the vehicle owner’s manual should always be the place to start your search for the right engine oil. You might find an ACEA rating quoted, followed by a manufacturer specification, such as ACEA C3 VW 504 00/507 00. In that example, the manufacturer uses ACEA as the base quality standard but requires enhancements to safeguard the performance of the vehicle. As such, technicians should prioritise the manufacturer specification, not just the ACEA specification. The VLS recommends that you consult with your PatFluid ad 130 x 92 new_Pat Fluid ad 130 x 92 17/02/2020 17:46 Page 1 lubricant retailer, or use one of the comprehensive online oil databases to help you make the right selection.


Technicians are told repeatedly that the lubrication requirements of modern engines are increasingly discerning. Therefore, filling the sump with an incorrect lubricant is not an option, because it can have serious consequences and can even void manufacturer warranties. Getting your oil choice correct, therefore, has become ever more critical.

In practice, not every technician is comfortable rifling through an owner’s glovebox, even if the handbook is present and correct. Yet, virtually many major lubricant blender/retailer hosts an accessible online database, where entering the car registration brings-up oil that complies with the relevant technical specification. These databases are not simply made-up by marketing departments but are powered by the expertise of respected organisations, such as OATS (based in the UK), or Olyslager (of the Netherlands), both of which spend many thousands of hours ploughing through service documentation to identify the right products.

We should be unsurprised, therefore, that quality oil blenders have paid increasing attention to ensure that their products meet the technical requirements but are their online databases all the same and sufficiently clear? To find out, AT conducted a brief experiment. We entered the registration number of a three years-old Suzuki Baleno 1.0-litre BoosterJet GDI, after Suzuki GB revealed the two oil specifications it recommends for the UK, and compared it to the results suggested by several popular databases:

1. Powered by Morris Lubricants, the OATS lubricant advisor was the clearest checker we found, recommending one product, with a single alternative.

2. Shell’s Lubematch offered a single offering that matched Suzuki GB’s requirements.

3. Fuchs’ oil chooser service-links/oil-chooser was not quite as succinct. Its three main options included the two recommended by Suzuki GB, with a further six (many with different viscosities) suggested on a drop-down menu. A Fuchs representative explained why: “There are some vehicles that can list a large number of specification/viscosity options so, whilst confusing, this is correct. To simplify this, on the FUCHS website, we initially state three results but also include a drop-down box where other suitable grades are listed. The latter is less common now than a few years ago and we would expect this to become even less common in the future.”

4. Castrol’s lubricant adviser is accessed via a link on the
Race Group’s website: https://castrol-ambassador. For our example, it listed twenty options, including two recommended by the OEM. The Race Group, the UK’s first Castrol Ambassador Distributor, could not explain why our finding might cause confusion but Castrol told us, while it cannot comment on individual car manufacturer requirements, the extra choice can be helpful, because: “Most OEMs want to ensure that consumers can readily obtain an oil for their vehicles, so provide for a range of specifications and viscosity grades. Tools like the selector will often throw-up every product that meets any of the specs, or viscosities, required by the OEM.”

5. LIQUI MOLY’s oil guide listed 25 options. The company explained why the extra choice can be positive, rather than confusing: “All of the oils listed in the oil guide are perfectly suited for your car. There are specifications suited only for a small number of models and there are specifications required by many models from many makes. If your car rather belongs to the latter category, then we have several oils, and all of them are good to use. Facing such a long list of search results allows you to further narrow down your selection. For instance, if it is an older car with a higher oil consumption, you may pick a higher viscosity oil from the list to reduce oil consumption.

“Some specifications can be combined with other specifications. Other specifications are rather unique and cannot be combined. We carry many different oils with different sets of specifications. This allows us to create individual selection of engine oils for garages according to their customer base. This reduces the number of different oils required, which facilitates purchasing and storage.”


Burning deteriorated fuel hastens engine oil deterioration. As petrol and diesel ‘go off’ within weeks, BG Products recommends that its in-tank additives, BG Ethanol Defender and Diesel Fuel Conditioner, are dosed into brimmed tanks of cars that are not used regularly. Kalimex (the UK distributor of JLM products) recalls reports of excessive DPF soot levels during the first lockdown, which obviously affects engine oil condition, and it recommends JLM’s DPF Cleaner fuel additive for all but the most severe of blockages. Lucas Oil reported that not only did sales of its fuel stabiliser increase but also fleet operators turned to the company’s ‘Heavy Duty Engine Oil Stabiliser’, sales of which also increased through motor factors and online channels. The main advantage of the oil stabiliser is to reduce dry-starts and keep oil covering the vital parts, to prevent corrosion that is caused by condensation. This is more likely, should we experience lockdown situations during the autumn and winter months.


BG Products has performed research on how modern engines are affected in the real world; a chief problem is a loss of compression from deposits building behind their low tension piston rings, a consequence of which is reduced oil longevity. It sees a decent engine flush (such as its EPR product) as key to removing these products and restoring combustion in a non invasive way. The company cites data from fleets that have experienced a decrease in DPF problems (among other benefits), since treating their vehicles with additives to protect the integrity of the piston rings. At the time of writing,

Castrol has just announced its new ‘shampoo’ oil flush, in part developed due to the company not recommending the use of solvent-based flushes, on the grounds that the company alleges that they can damage oil seals.

Choose oil fortifiers with care. Some companies insist that they complement the oil’s chemistry, others state that it upsets the delicate balance. Apply judgement, based on the car owners and the vehicle’s usage patterns. For example, as certain oil drain plugs can be positioned above the base of the sump, the remaining old oil will contaminate and reduce the life of the fresh lubricant. In such cases, a supplement may be the ideal solution.

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