Jerez witnessed the track debut for the upgraded Renault power unit that will power Red Bull and Toro Rosso in 2015.

Both teams were equipped with the upgraded Energy F1 power unit, which features - amongst several other changes - a heavily modified internal combustion engine, turbocharger and battery.

The focus of the four-day test was to test the new upgrades with the chassis package in representative conditions and to cover as much mileage as possible. After four intensive days both teams covered a total of more than 2,400km, or more than eight race distances, giving a solid footing going forward to the next test in Barcelona in two weeks.

"We've wiped the slate clean this year and have new, aggressive targets," said Remi Taffin, director of operations. "This week was the first step and we have hit nearly all the objectives we set ourselves. The primary goals were to fully integrate the power unit into our partners' chassis, eliminate the gremlins and then run as much as possible. We covered more than 2,400km over the two teams, which we can be relatively satisfied with at this stage. The Toro Rosso has been running particularly well and is representative of the mileage we need to achieve this season.

"There have been some teething troubles," he admitted, "which have arisen largely because we have been so uncompromising with our aims over the winter. The energy store in particular was being run as aggressively as we could, but we need to explore the limits of the parts in Barcelona to know how far we can push them. Likewise, a water pump issue was due to a relatively young part we tested on track rather than running extensively in the dyno - we are conscious that we need to pull out all the stops. We have learnt a lot from the running and have now put in place measures to prevent any further problems of this nature going forward.

"We have also had the opportunity to run our new trackside structure. This year we will have one extra person, with a track support leader overseeing engine performance rather than running one driver. It has made things easier and gives us the liberty to investigate other areas for performance.

"With our targets generally hit, we can look forward to the next test in Barcelona. We want to move more to the performance aspect of the power unit in this test and run in a specification closer to that we will run in Melbourne, of course still keeping a very close eye on reliability."

"The test this week has been productive and has confirmed that we have taken the right direction with our development choices," added Cyril Abiteboul, Renault F1 managing director. "This is reassuring considering the magnitude of the late clarification in regulations with tokens and so on, and how many times we have had to reconsider the various strategic options.

"Yes, we have had a couple of problems, but there have not been any nasty surprises. They were largely due to the fact that, taking our inspiration from the F1 teams, we have tried to push every design decision to the last possible moment to gain as much information as we could. Necessarily this means we experienced some issues on track. However all the issues are understood - and some were even anticipated - so we haven't suffered any setbacks.

"It's impossible to say where we are relative to the competition as others are running different plans, tyre specs, fuel loads, and even to a certain extent car specs etc. but our own performance level is where we expected. We have measured it very precisely in the dyno and it matches what we see on track. However just as the cars will be changed in Melbourne, our power unit will also be very different in a month. Reliability wise Mercedes are still the head of the table but we have had a positive week with Toro Rosso and will hopefully achieve this with Red Bull next time out."