The importance of using the correct engine oil

The importance of using the correct engine oil

Do you remember when automotive workshops had a big tank of oil that provided the lubricant for pretty much any vehicle that made it onto a service ramp?  Then it all changed as Euro Standards for emissions were introduced and an evolution in lubrication started to take place. Today as the drive towards Euro 7 compliance is starting to bite and hybrid systems are now commonplace, vehicle hardware and lubricant formulators are being pushed again into new territories.     

We are now seeing the next phase of evolution in passenger car engine oil technology with a move to even thinner grades to satisfy legislation that is driving down the level of CO₂ and lowering general emissions down to the next level.  There may still be a demand for 5W-30s, but 0W-20s, 0W-30s, 0W-16s and even 0W-8s are on the increase. OWs provide improved cold start fluidity, helping the oil to circulate more readily when cold, thus reducing internal drag on start-up, therefore using less fuel and ultimately producing less CO₂ emissions.  Thinner SAE 0W-20s, 0W-16s and 0W-8s offer reduced levels of internal friction at running temperature, once again making the engine more fuel efficient and reducing CO₂ output. But, as with their 5W-30 predecessors, each OEM has a different take on the finer points of engine protection and performance. 

Remember, however, we are purely talking viscosity here and not performance level. These lower (thinner) viscosity grades, together with friction reducing materials have taken a big step towards improved fuel efficiency (by reducing internal drag), but we have also seen an increase in the number of OEMs putting their stamp on these products. We have seen the likes of BMW, VAG, PSA, Ford and many others demand attributes that have resulted in the fragmentation of the passenger car engine oil market.

If that wasn’t enough, there is a new phenomenon known as LSPI (Low Speed Pre-ignition) in petrol engines.  As OEMS have moved to improve the fuel efficiency of petrol engines, smaller and smaller units have been subjected to turbocharging and supercharging and increased injection pressures. In these engines the effect manifests itself at low speeds during a burst of rapid acceleration. Premature detonation of the fuel/air mixture causes an abnormal peak in cylinder pressure which can, in extreme circumstances, cause severe engine damage. The solution to this new problem lies in modifying engine design, engine oil formulations and fuel quality. All the major OEMs have now adopted new lubricant testing protocols to ensure that the latest oil formulations do not promote this issue.

Hybrid vehicles and engines with stop/start regimes also pose challenges for the engine oil, where fuel and water dilution can lead to issues such as oil pump wear and bearing corrosion. Therefore, the engine oil is specifically designed to work within these demanding duty cycles.

There is now a large population of engines out there fitted with after-treatment devices allowing them to comply with the latest emissions legislation in terms of exhaust gas quality.  Diesel engines may be fitted with diesel particulate filters (DPFs) and Adblue systems, petrol with gasoline particulate filters (GPF) and of course three-way catalytic converters (TWC). All of these after-treatment devices rely on the correct oil chemistry to ensure their operational efficiency. Lubricants that create a high level of ash (formed when a small portion of lubricant is burnt is the combustion chamber) will prematurely block DPFs and GPFs. Lubricants with high levels of certain additive elements (sulphur and phosphorous) will poison Adblue catalysts and TWCs, making them ineffective. Car owners can’t get away with using the incorrect oil, as electronic sensors are continually feeding data back to the engine management system.  When things start going wrong, it may select a reduced power mode (limp mode) or stop the engine from starting altogether, until the problem is fixed.

The good old days of one oil to fit everything has gone and despite everyone’s best efforts to simplify the situation, there is still a high degree of differentiation required. Beware of lubricants purporting to be the answer to this complex situation, with a long list of OEM qualifications. There is no simple answer.

The correct oil is a critical fit and helps to ensure the operational efficiency of the engine, protection of aftertreatment devices, fuel efficiency and reduced emissions. It will also provide components with the optimum levels of protection between services, reducing the likelihood of expensive damage and inconvenient downtime. Always seek technical advice on lubricant selection as a tailored product may be required. 

Unsure what oil you need then call the Morris Lubricants Technical help on 01743 237541 desk or use the company’s whatoil feature on the website morrislubricants.co.uk, simply enter a registration number for a vehicle and the ideal oil is shown.

Blog by Adrian Hill, Technology Manager at Morris Lubricants.