As the rules constrict ever more tightly around opportunities for innovation in Formula One racing, the few remaining free areas, even seemingly trivial ones, gain unexpected potential to provide teams an advantage over their rivals. So team Vodaphone McLaren Mercedes found as they worked with technical partner ExxonMobil to develop a formula for Mobil 1 engine lubricant that was optimized for F1’s durability requirements while releasing as much of the engine’s power as possible.
Teams’ engine-design specifications were frozen by regulations at the end of the 2007 season, with changes permitted only for durability reasons. "As a consequence of the significant restrictions by the new engine rules, the significance of fuels and lubricants has, of course, increased," observed Norbert Haug, Vice President of Mercedes-Benz motorsport. "As everywhere in Formula One, we explore the practicable limits."
Of course, ExxonMobil thought it already had a pretty good racing oil, so it had to reconsider its status quo. "The engine freeze challenged us to re-examine our conventional understanding on how the oil can make a difference to the engine performance," remarked Bruce Crawley, Mobil 1 Motorsports Technology Manager. "We have to formulate Mobil 1 engine oil to get the balance exactly right between friction reduction and wear protection," he said. "It is all about attention to detail."
Which details? The specifics are closely guarded, but the company does say that a new synthetic ingredient helps trim friction losses inside the engine.
And why wasn’t the old oil already optimized, considering that ExxonMobil has provided McLaren with Mobil 1 for 14 seasons now? It was because the engines using the oil were a fast-moving target, with frequent upgrades and changes, explained Crawley. "The engine freeze was a blessing because now we have a stable engine, and surface finish tolerances were frozen," he said. "We were always chasing changes on the mechanical hardware side."
At the same time, the engine is carefully designed to complement the lubricant used, he said. "In the past, we’ve had the opportunity to change the mechanical side to adapt to the lubricant or to further exploit the performance attributes of the lubricant," said Crawley.
Lubricant is critical to engine performance because internal frictional losses subtract 15% of an engine’s gross power. "That is a lot of horsepower," Crawley noted. The bulk of these losses are due to the friction of the piston rings sliding through the cylinders and due to the engine bearings, with a smaller amount lost to opening and closing of the valves, according to Crawley.
Friction modifiers in the oil help address these areas, within the limitations of the oil’s ability to withstand pressure. "The joker there is durability," Crawley observed. If that is compromised, the power gains are worthless.
The McLaren team and its ExxonMobil partners, therefore, test extensively to verify durability through bench testing of engines before testing the oil in a racecar. This testing helps to confirm computer modeling that is used to predict the lubricant’s characteristics and the resulting performance improvement.
Compared to the major sources of friction, windage losses in the lubrication system are small but are nevertheless significant, said Crawley. "You actually lose some efficiency due to frictional losses occurring in the oil film itself," he explained. "This is what is sometimes referred to as internal fluid-film friction," he added.
This is the area of the company’s latest advance with its new unspecified synthetic component. So secretive are competitors that ExxonMobil doesn’t even patent its advances for fear of tipping off other teams about what it has done.
Putting the oil in the racecar is the culmination of three stages of research ExxonMobil conducts continuously. Short-term work is focused on getting a change into the car as soon as possible, while medium-term research examines promising developments and prepares them to become candidates for use on the track, said Crawley. Long-term research is "what-if" examination of future possibilities, perhaps with future engine regulations in mind, he said.
When developments progress into the short-term program by showing clear benefits, then it is time for durability testing to ensure the change can be made without compromising the team’s ability to finish races. This is where first dyno tests and then track tests are employed.
But the important thing is, once the latest advance in oil reached the track for a race, was the car really any faster than it would have been, just because of a new oil? "It was worth a lap-time improvement," asserted Crawley. How much? "That sort of information is kept proprietary."