The Grumobile is a large, rocket-powered vehicle that is used as the primary means of transport for Felonius Gru.
The vehicle has the super high position (approximately equivilant to one-story high) for its seats. Under the seat, there is a large space for several people (as seen when Gru takes his daughters into it), and a door is placed behind the vehicle. It can speed up instantly, and the sound of the honk is low comparing to ordinary cars.
After getting a cup of coffee, Gru drives home in his Grumobile; in his way, he overtakes a man who just overtook the slow car that Gertrude drives. Then, when he heads to the Bank of Evil, he pushes cars out of their parking spaces before parking. Gru later drives the Grumobile away from Miss Hattie's Home for Girls after adopting the girls, and the flame burns a child's balloon in the process.
Some days afterwards, Gru parks near Vector's Fortress before breaking into to the young supervillain's home to retake the Shrink Ray. After the heist, Gru drives the Grumobile to Super Silly Fun Land.
Despicable Me 2
Gru heads to Eduardo Perez's Cinco de Mayo party with the Grumobile, smashing all cars parked outside the mansion. He later drives back home quickly after giving excuses to Eduardo when he gave him a chance to conquer the world with him, and the fence between his and Fred McDade's house is smashed before the vehicle parks into the yard.
Edith is seen riding around on a miniature riding toy version of the Grumobile in the girls' bedroom.