• You can store up to 9 seconds of turbo. The amount of turbo given by each box increases for each race where you have previously used turbo.
• If you use turbo before a jump, you can can continue at speeds above the top speed until you land. You can get more use out of your turbo this way because you don't need to use any turbo while flying.
• While using turbo your car's handling is improved. This makes it faster to wiggle when using turbo instead of driving straight. You can also use turbo more efficiently by saving it for sharp turns.
• Toolboxes respawn 2 minutes after they are picked up. Try to pick up blue tool boxes early so they will respawn faster.
• The first time you pick up a blue toolbox which has respawned, it will unlock paint options for your current car instead (if not already unlocked).
• Use turbo on laps where your power meter is low to make up for your lower speed and quickly get power back.

Here is how I use these tricks for my current All Cars route:

Tiki Jungle

If you get turbo here, it will increase the available turbo on Beachway from 9 seconds to 18 seconds. Grab the boxes on checkpoints 1 and 3 immediately so they respawn sooner.

Beachway

The opponent cars rarely grab the checkpoint 2 or 3 boxes, so you can skip the checkpoint 2 box until you have used the turbo from the other checkpoints. Save some turbo for lap 7 when you power down. Wiggle on the straightaways for extra speed.

Construction Site

Using turbo for an entire lap will bring you back to the moving doors at about the same point in the cycle as they were when you left. Try to hit the moving doors on lap 2 right as they open and then turbo through the rest of the door cycles. Use the previously mentioned tricks so your turbo lasts until lap 6. Use any leftover on lap 7 when you power down.

Moon Base

Go directly to checkpoint 1 when the race starts. The opponent cars will sometimes not pickup the blue toolbox at checkpoint 2, so don't pick up this box until after you have used the turbo from the other checkpoints. Then, don't use all of the checkpoint 2 turbo right away or you will pass by the boxes on lap 7 before they respawn.

Asteroid Belt

Again, you can skip the checkpoint 2 box until you have used up the rest of the turbo. Use turbo on flying sections to get the best use out of it.