Alonso set the car's quickest lap of the “Roar Before The 24” test in Sunday's prequalifying session, but was only 12th fastest and 1.7 seconds off former F1 rival Felipe Nasr's pacesetting time in the Action Express Cadillac.

"There are still little changes going on and it's the same with the performance of the car," said Alonso. "Obviously it's early days, it's only testing, but we need to find more pace and hopefully be more competitive when we come back in the race."

The three-day test was dominated by the Cadillac DPis, with the Action Express, Wayne Taylor Racing and Spirit of Daytona teams splitting fastest times across the seven sessions.

Alonso said his priority during the weekend was to get used to sharing the car with teammates Lando Norris and Phil Hanson. He admitted it had been hard to fit all the required work into the test sessions, which varied from 45 minutes to two hours in length.

"The amount of laps is not huge but it's better than nothing and I feel more prepared now for the race, for sure," said Alonso. "It was a good weekend to work with the guys, with the team, with the teammates and enter into this mood of sharing everything and adapting and making compromises between all of us to be happy all around.

"That was the main priority for the weekend and it's what we achieved. That was a positive thing.

"Probably the biggest surprise was the little time that you spent in the car. The sessions were not very long and you share the car so you lose a little bit of time in the driver changes, in the set-up changes and you ended up doing very few laps.

"That was maybe the surprise and what I was missing this weekend but I think that's part of the game and in the 24 Hours we will accumulate enough laps for sure."

Alonso had expected the night-time driving and dealing with traffic from slower cars to be the main things to adjust to, but found both straightforward.

"It was no big difference compared to the daytime," he said of Saturday's after-dark running. "Also in F1 we have some night racing in Bahrain, Singapore and Abu Dhabi. The circuit is quite well illuminated here, it's maybe not like other endurance circuits so I found no big issues there.

"Same with the traffic, that I was a little bit afraid of. There are always some moments and some risks when you are overtaking cars here and there or if they are fighting each other but that's a normal thing that everybody will face, not only us the rookies. So that's something that we should be on top of for the race as well."