With much of Friday's running washed out the team was not able to get in the mileage they had hoped for on day one at the Spa-Francorchamps circuit.
As such Grosjean says his team will wait until Saturday to make a decision.
"We will see what we can do tomorrow," the Frenchman told Autosport.
"I don't know what is decided yet, if we keep it on both cars or only one car.
"For sure it was not the best conditions and we needed some dry weather to see if it was working as expected, but tomorrow we'll maybe keep it for P3 and then we take the decision."
Asked for his thoughts on the whether the double DRS should be raced for the first time, he said: "I think the best decision has to be taken by the engineers, but honestly on my side it is the same if I use it or not.
"Hopefully the performance is good without the upgrade and we'll have an easy solution.
"Nobody knows where we are. Let's see tomorrow in P3.
"It will be a hard work session but by then we should know a bit more about performance and if we want to take a risk or not."