With Friday's practice heavily affected by the weather, the team decided against running the new system for qualifying and the race.
And despite qualifying a disappointing ninth, having narrowly scraped out of Q1, Grosjean says it was the right call.
"If yesterday we could have used it on intermediates, then maybe we would have raced it on one car," he said.
"But today it was the best choice to not run with it."
According to Grosjean, the lack of dry running also took its toll on his ability to learn on his first Formula 1 appearance at Spa since 2009 - which showed in the qualifying session.
"It's not quite what I wanted," he said. "It was not the best qualifying session of the year, that's true. It was difficult with the lack of running, especially when you're a rookie here. Spa is a very difficult track."
Despite the fact that he will be starting in the thick of the traffic, Grosjean has also pledged to turn the tide on his ongoing run of lap one incidents at Spa.
"The initial bit of the start will be crucial, and then everybody will brake at more or less the same place into La Source," he said.
"Then there is a long straight, so you can maybe use your KERS in a different way. It will be interesting.
"But we know overtaking is quite easy here, so there is no reason to play everything on the first lap."