What’s with these low-viscosity engine oils?

A reasonable question! Given all we have discussed so far, the engines must be small, light, have decent longevity, and put out more power per cubic litre. They must also make great torque to couple up with a DSG gearbox, a CVT or a multi-speed (as many as ten gears) conventional auto transmission to produce the fuel economy and drivability the driver demands. 

The 0W-20 oil now plays the role that 5W-30, 10W-40, 15W-40 and 20W-50 viscosity engine oils have played previously. Its main role will be maximising fuel efficiency with excellent lubricity. Effectively, lubricity translates over time to low engine wear and long engine life.

To enable a long engine life, the oil must: 

• Be compatible with catalytic converters for petrol and LPG/CNG fuelled vehicles. 
• Be compatible with light diesel exhaust after treatment – namely Diesel Particulate Filters (DPFs) and Diesel Particulate Diffuser (DPDs).
• Enable trouble-free action of EGR (Exhaust Gas Recirculation) valves for petrol and diesel engines.
• Have the correct viscosity characteristics to suit the engine design regarding internal clearances plus minimum and maximum tolerances.
• Have the correct friction reduction characteristics, which stimulate power production, reduce heat build-up and require minimum effort to pump around the motor constantly. In other words, have excellent fluid dynamics.
• Resist evaporation and combustion burn-off to meet the OEM’s oil consumption expectations. From the consumer’s point of view, reduce oil top-ups between services.
• Have the correct additive chemistry and base oil characteristics to minimise combustion chamber deposits, leading to the new LSPI or Low-Speed Pre-Ignition phenomenon. This phenomenon occurs in new technology down-sized turbocharged petrol engines with direct fuel injection. 
• Protect the timing chain and other engine components from premature wear. 

LSPI is a discussion point all on its own. It is, however, very relevant to 0W-20 viscosity PCMO’s. So what is LSPI and how do 0W-20 engine oils help to defeat it? LSPI is Low-Speed Pre-Ignition. Pre-ignition appears to the driver as a knocking noise coming from the engine under instantaneous acceleration from a low road speed situation. The vehicles that are most prone to LSPI are petrol engines in the 1000cc capacity range that are highly turbocharged and have direct fuel injection. 

The root causes of LSPI are not fully understood and remain somewhat of a mystery; however, it is thought that it is, in part, oil-related. The source of the knock is thought to be a combination of soot accumulation, combustion chamber hotspots and/or combustible material fuel and/or engine oil igniting within the combustion chamber, igniting prior to the sparkplug firing. High pressure and high-temperature conditions also need to be present for it to occur.

Contributing factors are fuel quality, engine oil formulation, engine design, valve timing and effectiveness of devices such as knock sensors and similar. These provide data to the vehicle’s ECU to vary ignition, fuel injection timing and valve timing in order to stave off LSPI and other forms of pre-ignition and detonation before it can do damage and, of course, lack of scheduled maintenance. The confounding part of LSPI is that it appears to be largely unpredictable and occurs randomly.

When we look specifically at engine lubricating oils that contribute to LSPI, it is microscopic droplets of oil sourced from the cylinder wall, piston rings and inlet valve areas of the engine combined directly with injected fuel and air under high temperatures and pressures. Oil is known at least to be a contributing factor in LSPI and thought to be a reason behind its random nature. Again, LSPI is yet to be fully explained, but we know the when, where and why. The hows are under continued investigation.   

Damage from LSPI is quite catastrophic. It can result in broken and/or melted spark plugs, holes in pistons and damage to cylinder walls. Piston-related damage from excess pressure and uncontrolled combustion may include broken rings, connecting rod damage and bearing damage. Total engine failure is also a real possibility. The potential consequences of unchecked LSPI are significant and costly to repair; however, there are some solutions.

These include:

• Always use high-quality, higher octane (RON) fuels – they are more stable and less likely to self-combust.
• Use an LSPI-compliant formulation engine oil. 
• Use fuel systems and injector cleaners regularly – they reduce deposit formation in the upper cylinder area.
• Keep up scheduled maintenance at all times. 

Workshops should be on the lookout for anything that is likely to affect the normal and most efficient operation of the engine. 

Speaking of engine oil and how it has needed to evolve to cope with mitigating LSPI, proactive oil manufacturers like us are constantly evolving our products to meet the demands of the newest vehicles. We collaborate with base oil refiners and additive manufacturers to bring the latest technology engine lubricants into our range, enabling us to serve the newest makes and models as they are released. 

Utilising the best base oil options is a given. Having best-in-class base oil ensures that the most fundamental lubricant function and boundary lubrication (where an oil film separates sliding surfaces or those that may touch together) are well covered. The next ingredient, the performance additive, has been fully researched, tested and proven for LSPI protection.

To help defeat LSPI, we have selected the best-credentialed low-calcium formulation additive concentrates from major manufacturers who have proof of performance concerning LSPI.

As well as the many other criteria a state-of-the-art engine oil must meet. Rounding out the equation are our blending processes, QA requirements and pre-sale laboratory testing. “Near enough is not good enough”.