Renault Sport managing director Cyril Abiteboul believes Red Bull's use of an alternative fuel supplier could be hurting them achieve maximum performance from the engine.

While the French manufacturer and McLaren use BP Castrol for their fuel and other lubricants, the Milton Keynes outfit has Exxon Mobil after the company actually switched from McLaren during their Honda woes.

That means that while development of the engine and lubricants is undertaken with both suppliers, it is BP Castrol that get greater priority and as a result, could see Red Bull lag behind a little.

“I was secretly hoping that Red Bull would have the pace to win,” Abiteboul told Autosport after they brought an upgrade to the Canadian GP last weekend.

“They were very, very close to that, but not quite there. We have more to come, and they could have more to come from the fuel.”

Currently, there is greater tension between Red Bull and their supplier as they consider whether to stick or switch to Honda for 2019, with Renault threatening to leave them no choice but to change if a decision isn't taken soon.

That could be why Abiteboul is looking to divert some blame away if the Anglo-Austrian squad feel the upgrade didn't work as well as hoped, but as the Frenchman pointed out, it is their own decision.

"Something that is clear, we can guarantee an equity of performance of what is in our control, which is hardware, which is software,” he continued.

“They elected themselves for strategic and commercial reasons to go for their own [fuel and lubricants] partner, which we appreciate and we support by homologating their product,”