FOCUS: FLUIDS E FILM STARS very kilometer of range and gram of CO 2 counts in today’s automotive world, which means transmission efficiency is more important than ever. At the same time, alternative powertrains are rewriting the rulebook for transmission design, with fresh concepts, new materials and increasingly challenging operating conditions. It’s the most disruptive period in the automotive industry for more than a century. Driveline fluids have a significant role to play in this brave new world – not just in supporting the wider drivetrain concept but also in the efficiency improvements they can bring in their own right. To illustrate this aspect, Thomas Hellwig, head of product development for EV transmission fluids at Castrol, points to comparative testing that the company has recently carried out on two drive fluids. “If you use an optimized fluid, which we recently developed, and you compare it with the standard fluid, we are able to gain more than 1% [vehicle] efficiency over a standard drive cycle,” he comments. “In this context, 1% is huge because we’re talking about a drive unit that already has an overall efficiency of maybe 93 or 94%.” This single change would be enough to have a measurable impact on battery range in an EV, and potentially at a far lower cost than achieving the same benefit through design changes to the battery or motor. “It’s not just the efficiency of the gearset but the thermal optimization of the motor,” notes David Kupiec, head of performance fluids at TotalEnergies Lubricants. “We see 30 Transmission Technology International / 2023