When hybrid engines were introduced a ban on in-season engine development was introduced to cut costs. However, Ferrari found a loophole in the FIA rules and as a result all teams aside from new entrants Honda are able to stagger development of their engines. This will not be the case next year though, as the FIA have tweaked the rules to ban it.
With Renault currently some way behind rivals Mercedes and Ferrari, they will have limited scope to improve next season if in-season changes are not permitted.
Renault Sport boss Cyril Abiteboul has stated that the manufacturer will not remain in the sport if they do not have a competitive engine. With Renault's contract with Red Bull and Toro Rosso set to expire at the end of 2016, Horner believes that they may not have the chance to become competitive once more and as a result the French outfit may exit F1.
At present, teams need to submit the designs for their 2016 engines by February 28, and a unanimous decision would be required for the rules to change, with Mercedes unlikely to go along with any changes due to the dominant position that they have carved out.
However, Horner feels that the change would indirectly be in Mercedes' favour as Renault's exit would be detrimental to the sport as a whole.
“The situation is we are at a precarious point in terms of Renault’s commitment to the future,” Horner said.
“If you are effectively shutting that down (the engine development) in February, you are almost waving goodbye to them.
“So (Mercedes) need to have a bit of a grown-up think about it. And the FIA as well to say what is in the best interests of F1. If F1 can afford to lose an engine manufacturer, then stick to February 28.”