Mercedes introduced the upgraded car for last weekend's race in Monaco, with changes to the sidepod and suspension, but the nature of the slow and twisty street circuit made it hard to draw any conclusions.
"You can't really tell a lot from Monaco, you would never choose to test an upgrade at Monaco," Hamilton told reporters at the Circuit de Catalunya on Thursday.
"This is a perfect test track, a lot of medium and high-speed corners, so we should get a real good understanding of where we stand compared to the others.
"From what I felt at the last race I'm really intrigued to see what it feels like here, because I think our race was pretty decent last year here, even though we had the puncture at the start."
George Russell was third for Mercedes and Hamilton fifth in Spain last year.
Mercedes have been playing catch-up since the start of the season, with champions Red Bull way ahead of the rest and winners of all six rounds so far. Aston Martin, who use Mercedes engines, are still ahead of the works team in the constructors' standings.
Mercedes are not the only ones to have upgrades, with Ferrari also hoping to pick up some pace with their latest package and Aston Martin and Alpine bringing developments.
Red Bull consultant Helmut Marko told Austrian media that his team would also be trying something new in Barcelona but championship leader Max Verstappen played that down.
"I think Helmut got a bit excited as well, so I don’t know," he told reporters. "We just do our normal program and nothing crazy."
