Toro Rosso won't use upgraded Renault engine in 2015

Renault has used 11 tokens to develop its power unit and has made it available to both Toro Rosso and sister team Red Bull.

However, Toro Rosso believes that it is not worth using the new engine as it would mean having to take extra grid penalties.

The Italian outfit has enough examples of the current spec to get to the end of the season.

"We're going to stick for the rest of the year with the old spec," said Carlos Sainz.

"Given the [performance] values that they've given to get another grid penalty and start last, especially with the last four tracks, they are similar to this one...

"Okay, they are not the best tracks because they have long straights, but it's not the worst, so we can be very close to the top ten, so to start last, I think it's too much, it's not worth it, so we will commit to this year's spec that we have now, that's good enough to finish the year, and we have plenty of them.

"It's an important end of the season now, because we have four races that the tracks should not be bad for us, and we lost a lot of points from the middle of the season, particular me.

"We need four races where we can qualify decently and race hard from the top 10. So I don't want to take more penalties to be honest."

Meanwhile, teammate Max Verstappen suggested that the team would keep an eye on how Red Bull performs when it runs the new engine.

"I think we have to wait and see how much the difference is," said Verstappen. "So we have to wait and see how what Red Bull does with the engine, if they are going to use it or not here, and what the difference is.

"If it's not that much and you take again a penalty then your race is a bit more difficult again. We just have to wait and see. And if it's good then hopefully we will have it soon as well."