Red Bull have snatched a top, long-term sponsor from F1 rivals McLaren, it has emerged.
Two weeks ago, it was reported that the British oil multinational BP is looking at returning to the grid, with McLaren and Renault both in the running.
It now emerges that McLaren wants a new oil backer because it is losing 21-year partner Mobil to Red Bull.
"There are rumours of arguments with team management, because the price-performance ratio was no longer right," said Auto Motor und Sport correspondent Michael Schmidt.
He added that the loss of sponsors and the lack of replacements is one reason McLaren supremo Ron Dennis is clinging to his current position.
Schmidt said that the new BP-Castrol deal is less lucrative than the Mobil one, and could actually cost McLaren-Honda in performance due to the switch to new and less developed petrol and lubricants.
