I have read on the wiki that vehicle health scales for 5 level intervals of your level (5,10,15, etc.). Is this true for other vehicle stats (boost time, boost speed, damage)? Because when I'm car-fighting enemies that have scaled up in level since I last fought them, I feel like I'm still killing them just as fast.
Only boost time is affected by certain Relics(affects Boost Time, Boost Recharge Rate, and Boost Delay) you can find through a certain Mission. Boost speed is never affected; Boost speed is relative to the vehicle you use.
For instance, the Runner boasts a higher boost speed than the Bandit vehicle, but has a shorter boost time than the Bandit to compensate, as well as having greater mobility. Note, none of these factors are scaled with level.
Damage will scale with the health of the vehicle, in accordance to whatever level the leader of the party is. If playing in UVHM, the level of the vehicles damage and health will scale to the highest leveled player in the party.
I hope this helps!