Boost is an upgrade for all vehicles.
Automatic boost gives additional speed for a small duration. Upgrade to increase boost power. A boost only lasts a few seconds so it isn't necessarily the best tool to use when trying to cover long distances, to cover long distances quickly you need to upgrade your tires. Boosts are only useful if you want to get over a steep hill, although better tires can also contribute to this. They start off as 30 diamonds but then they get more expensive every time you get another one. To avoid this buy only 2 boosts, use them then buy more otherwise you will use your diamonds way to quickly. However, after you get the garage, the only thing that you can do with diamonds is to get boosts, it really is your choice if you want to stock up.
There are 2 ways to use activate boosts, you can press the up arrow or you can click the boost symbol on the screen. Be careful not to click the up arrow when you don't want to use a boost, this can be really annoying. The boost button on the screen displays how many boosts you have.
An active boost should leave an electric blue trail after your vehicle. If you click the button but nothing happens, you have not activated your boost.
A boost can, unfortunately, unbalance your vehicle, which will make you die.