Renault has been given approval to make a "large" number of improvements to its engines for cost and reliability reasons, even though the FIA has ruled out any form of power equalization for this year.

The French auto manufacturer wrote to the FIA in the build-up to the season requesting a number of changes be made to its power unit – amid some suggestions that the FIA could even equalize engine performance for 2010. This comes after Renault's customer partner Red Bull Racing openly felt it was unfair that not all engines were equal, despite an engine freeze.

Red Bull Racing team principal Christian Horner said: "I think the problem is if you don't allow some development, then you freeze in an advantage for one team or a disadvantage for another. So there has to be a balancing of that, otherwise we will end up with Mercedes-powered cars winning all the races – which I think is not good for F1. And other manufacturers may choose to leave F1 off of the back of that.

"The engine isn't supposed to be a key performance differentiator and therefore, hopefully, the ruling body will balance out somewhat the differences there at the moment."

AUTOSPORT reports that the FIA decided against any move toward "equalization," because it felt there was not enough evidence to suggest there was a big performance difference between the various power units. However, Renault has been told that it can make a number of changes to its engine for cost and reliability reasons – with all its requests in this area being approved by the FIA.

It is understood that further changes that were requested, which would have helped improve Renault's fuel consumption, were rejected because these were purely for performance reasons – and not on the "fair" basis of the other changes that are open to all car makers

Renault team principal Eric Boullier said about the changes: "Like every manufacturer here, we have some allowance to fit our engine and have a better integration with the chassis. So, I think, out of the changes that were requested – some of them were quite tricky, so the FIA was not positive, but I think most of them have been approved."