Formula One has two safety cars which alternate at races, an Aston Martin V8 Vantage and a Mercedes-AMG GT Black Series.
The Aston Martin car produces 528 brake horsepower compared to the 730 brake horsepower of the Mercedes car.
While a Formula One race is neutralised behind a safety car, drivers still have to keep their tyre temperatures at an optimal level in order to have enough grip at the restart which follows. Drivers often weave their cars from side to side during these points of a race to get heat into the tyres.
Verstappen said the Aston Martin safety car is not fast enough for drivers to warm them effectively.
"There's so little grip and also the safety car was driving so slow, it was like a turtle. Unbelievable," Verstappen said after the race.
"To drive 140 [km/h] on the back straight, there was not a damaged car, so I don't understand why we have to drive so slowly. We have to investigate.
"The Mercedes safety car is faster because of the extra aero, because this Aston Martin is really slow. It definitely needs more grip, because our tyres were stone cold.
"It's pretty terrible the way we are driving behind the safety car at the moment."
Verstappen has had a very mixed start to his first Formula One championship defence. In three races, he has won once but retired twice while running in second position.
Verstappen is sixth in the standings and already 46 points behind early championship leader Charles Leclerc, who has won the two races Verstappen failed to finish.