Red Bull has lured McLaren's long-time oil and fuel supplier Exxon/Mobil away from the Woking-based team, as part of a major technical shake-up that will result in Castrol/BP returning to F1.
McLaren has worked with Mobil for 21 years, with the two companies having enjoyed four world championship titles and 78 race wins together.
However, more recent competitive struggles and the attraction of joining forces with Red Bull has seen the two companies conclude a deal, with Exxon/Mobil to provide fuel for the team's customer Renault engine.
Up to now, Red Bull has been using Renault's current partner Total, so will have to work hard with Mobil to ensure that their products work well with the French car manufacturer's power unit.
McLaren has wasted little time in sorting out its own situation, and it is understood to have finalised a deal with Castrol/BP to return to F1.
The switch of fuel supplier will provide a fresh challenge for Honda, whose engine so far has been built in close co-operation with Exxon/Mobil.
The major shake-up of oil/fuel suppliers could have a fresh twist, however, with Renault - which is ramping up efforts for its work team – also believed to be considering a move to Castrol/BP as well.
Neither McLaren nor Red Bull have commented on the deals, but sources suggest that announcements will be made before the end of the season.