Webber revs up for Cosworth's final bow.

The last race of any Formula One season is always one of farewells, with drivers and suppliers either leaving the sport or switching allegiances for the following year, but Interlagos will see a double departure at Williams, with Mark Webber and Cosworth both preparing to make their final appearance with the Grove squad.

In both cases, it will be a sad adieu, with Webber's supposedly dream move to the team that provided countryman Alan Jones with his world title having fallen flat, and Cosworth staring into the F1 wilderness as the team accepts a 'factory' deal with Toyota for 2007.

With Spyker MF1 having opted for a Ferrari deal over Cosworth for next season, and Scuderia Toro Rosso set to run either Ferrari or Renault V8s, the famous engine builder faces an uncertain Formula One future, despite having provided one of the higher-revving units of the year.

"The 2006 Brazilian Grand Prix is likely to be the last race for Cosworth as a Formula One engine supplier," head of race engineering Simon Corbyn admitted, "The objective from the outset of the CA2006 programme was to deliver the benchmark new generation V8 Formula One engine and, at Cosworth, we believe that we achieved that in terms of engine performance, reliability and also engineering support to Williams."

The company, which made a winning debut with Jim Clark in 1967, aims to go out on a high, however, with Webber able to take a fresh V8 for his, and Cosworth's, swansong.

"Mark will start the weekend with a fresh Series 6 engine, and will run an engine duty cycle specifically for Brazil, which will allow the engine to run at 20,000rpm for the entire race," Corbyn revealed, "We will be going all out to add to our tally of 176 wins in 39 seasons of Formula One."

The season has been a tough one for Williams, as reliability problems with the FW28 have seen Webber and rookie team-mate Nico Rosberg fail to trouble the scorers at a majority of races. With the past two years having not lived up to his lofty ambitions, Webber now leaves for Red Bull Racing, ironically the team - in its previous Jaguar Racing guise - that he left to join Williams.

"It's clear that it's been a long and tough season for everyone at Williams but, with one event remaining, we'll be doing our utmost to extract the best possible result from the package we have," the Australian said, attempting to put a brave face on the campaign, "Interlagos will mark my last race for the team and, of course, it would be nice to sign off with a strong result for the boys."

Technical director Sam Michael will be sad to see countryman Webber depart, having valued his development input, and also laments the parting with Cosworth, despite getting his hands on Toyota for next year.

"This weekend's race will be significant for the team for two reasons," he confirmed, "Mark has made a significant contribution over the past two seasons, not only on the race track, but he has also been a great team player and we wish him well for the future.

"It will also be Cosworth's last race with Williams, and we thank them for all their efforts this year. For everyone involved with the team, it would be a fitting reward to take some points away from the final round. It hasn't been the best of years for us, but we have taken all the lessons learnt on reliability and performance and are busy applying them to our 2007 car, where we aim to return to being a frontrunning team."