Toro Rosso-Honda is poised to agree a partnership with oil company ExxonMobil in the 2018 Formula 1 season, Motorsport.com understands.
As a result, McLaren-Honda did a deal to run Castrol/BP products for this campaign.
Toro Rosso ran Esso and Mobil products in 2017, falling into line with senior team Red Bull.
It was unclear whether Honda would continue with Castrol/BP on joining Toro Rosso or return to ExxonMobil.
But it is believed both sides were keen to pursue an arrangement with ExxonMobil, following past experience and recent rate of development.
Red Bull has been pleased with the gains Esso has made this season, with the team suggesting its latest upgrade delivered a performance improvement worth one grid slot depending on the circuit.
The supplier is aiming to introduce three fuel upgrades across next season as well as a series of lubricant improvements.