Although strong throughout his junior career, the Belgian rookie has regularly struggled to shine alongside teammate Fernando Alonso in 2017.
"I think everyone knows our weaknesses this year," the 25-year-old said at Silverstone.
"Because of the engine, we lose a lot of time on each lap, but the chassis itself is quite good. I'm not saying it's the best, but it's definitely very good."
Nonetheless, speculation that Vandoorne might lose his seat for 2018 has been rife, even though McLaren executive Zak Brown said this week he expects him to stay.
Vandoorne said: "I am not worried, because I signed a multi-year contract with the team.
"I like everything here, we are moving in the right direction, and I'm sparing no effort in working together with McLaren. It's my main goal and I'm completely focused on it."
McLaren's only two points this season have come from Alonso.