Better weather likely at Jerez on Thursday
"Fortunately the weather forecast looks a lot better," Renault's chief engineer Alan Permane confirmed.
It is particularly good news for Red Bull and Force India, whose 2010 cars made their debuts at the drizzly venue on Wednesday.
The new Virgin is also testing for the first time at Jerez, and on Wednesday lapped just 5 times in the hands of Timo Glock.
"It wasn't the time to push it and risk crashing. We would have compromised next week's test," the German is quoted as saying by Italy's La Gazzetta dello Sport.
But while Thursday is likely to be mainly dry, more rain is forecast for the final two days of the test on Friday and Saturday.
Renault intends to make the most of what could be the only dry day by reshuffling its schedule so that Robert Kubica takes Russian rookie Vitaly Petrov's place in the R30 on Thursday, and possibly beyond.
It is also rumored that if more days are affected by rain, another group test before March's Bahrain season opener might be scheduled.