Double world champion Fernando Alonso gave Renault's 2008 Formula One car an encouraging track debut on Monday ahead of next week's formal launch.
"When you have your first day with a new car you always have to take your time to check all the systems are functioning correctly and that is what we did today," said the Spaniard in a news release.
"Everything went well but it is still too early to try and compare our performance with that of other teams, and that was not the objective today.
"The good news is we encountered few problems and we will be able to continue our work tomorrow."
Alonso, who has returned to Renault after a troubled season with Mercedes-powered McLaren, completed 39 laps of the Valencia circuit in the R28 car after being delayed by morning fog.
"The car ran pretty much trouble-free, that is about as good a first day as you can expect with a new car," said chassis technical director Bob Bell.
"We would have completed our first run pretty much on time if it had not been for the weather and I think that's a real tribute to the whole factory and all the hard work that has been put in to get this car here today."
Renault, third last season after winning the 2005 and 2006 championships, will launch the new car in Paris on January 31. The season starts in Australia on March 16.
