Opinion 14 Oil is no longer a commodity it’s a precision component Alan Outhwaite, Head of the Technical Review Panel at the Verification of Lubricant Specifications (VLS), discusses the particular lubrication challenges posed by hybrid vehicles. Hybrid vehicles have grown in popularity in recent years and are likely to remain an important part of the vehicle parc for many years to come, despite the current 2035 ban on sales of new hybrid cars. For some motorists, hybrids offer the perfect balance – harnessing the benefits of battery power without the range anxiety of battery electric vehicles. Despite their similarities to internal combustion petrol and diesel engines, hybrid vehicles have some critical differences. The duty cycle of hybrid vehicles is quite different, with many more stop-starts as the vehicle switches between power sources. In hybrids, the engine may need to start suddenly at high speed, when the vehicle may already be travelling at 60 mph, having used battery power to begin the journey. Such high-powered cold starts give the engine no time to reach operating temperature, increasing the risk of thermal shock and wear, as the oil hasn’t had time to circulate through the engine to protect moving parts while the engine slowly builds up. Hybrid vehicles are likely to warm up more slowly in general. Typically, an internal combustion engine (ICE) takes up to 10 minutes to reach operating temperature, depending on its use. A hybrid vehicle could take 25 minutes. On shorter journeys, the vehicle may have arrived at its destination and been switched off before it even reaches temperature. This longer warm-up period provides more time for water and fuel to accumulate in the sump, increasing the risk of fuel dilution and emulsification, which could lead to corrosion and increased wear. It is therefore even more critical that motorists and mechanics follow the recommended oil change intervals. If an oil warning light appears, the driver must not ignore it but take immediate action. Along with lower viscosity, hybrid vehicles tend to require oils with lower High-Temp High-Shear (HTHS) values to further increase fuel economy. Workshops must also use the appropriate specification engine oil, looking beyond the viscosity to the actual performance specification. Modern high-power-density petrol engines can require specialist lubricant chemistries to minimise the chance of events such as low-speed pre-ignition (LSPI). Backwards compatibility with other applications cannot be assumed, so an oil suitable for a new hybrid vehicle may not necessarily be suitable for the older hybrids being serviced in workshops. If at all unsure which engine oil to use, it is always worth taking the time to double-check with the vehicle handbook and the OEM. Workshops should also monitor OEM updates regarding changes to service intervals and oil change intervals. These are both likely to be more frequent than with conventional ICE-powered vehicles, as the oil has to work in a hostile environment with regular short, cold journeys. Hybrid vehicles are relatively new compared to ICE vehicles. OEMs are, in some cases, still learning about duty cycles and their effect on lubricants. Motorists can no longer assume their vehicle requires service every 12,000 miles or 12 months. As we expect lubricants to do more, under greater stress, they may need more regular replacement. We expect lubricants to do more, under greater stress Alan Outhwaite, Head of the Technical Review Panel at the Verification of Lubricant Specifications
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