"I thought it was raining at one point," he told reporters. "It was very, very difficult.
"Over one qualy lap it is always a decent tyre," he said of the hypersoft, "but whenever you want to do a long run, you do three laps, and then it is like driving in the wet."
Friday, if you'll forgive the pun, witnessed a 'perfect storm', with the low grip track surface further compromised by high temperatures and the Mexico debut of the softest compound in Pirelli's 2018 range. As a result drivers clearly struggled to remain on the black stuff, with a number, including both Ferrari drivers, flat-spotting a couple of sets.
"The tyres were very difficult," agreed Grosjean's Haas teammate, Kevin Magnussen who ended the day uncharacteristically at the foot of the timesheets. "I didn’t get a lap on my hypersofts until the last lap of the run which by that time I couldn’t go faster any more.
"We are not last but we are certainly not as competitive as we want to be," he admitted. "On low-fuel it’s one story but on high-fuel it’s a completely different story. You’re just driving around, trying to stay on the road. You’re not racing, you’re trying to get around the lap rather than trying to go fast because you don’t have any grip. You might as well be driving in the dry on wet tyres. I don’t know why it’s so bad on this track but it’s certainly a big problem."
Check out our Friday gallery from Mexico City, here.