For Euro Truck Simulator 2 players, this guide provides instructions to prevent that the GPU usage goes up to 100% when you tab out the game.
Adjust graphics settings
If you uncheck the fullscreen mode, you play the game in windowed mode. This means that the vertical synchronisation (FPS lock) is not affected when you tab out the game.
There is no noticeable difference in the game between window mode and fullscreen mode.