Some sort of mechanic where when vehicles explode they move around or lift off the ground would be neat to see. Like some sort of randomizer so it doesn't happen every time the vehicle catches on fire. Like a small fire for example. This could only have the effect if the fuel tank explodes. And maybe bigger vehicles with more fuel could have a bigger explosion mass in the process and have the ability to push or move other vehicles around slightly. Edit: This is also a slight reference to B25Mitch's Explosive Propane Tank mod how if you hit it and it explodes it can send vehicles flying due to the explosion.
Maybe not for cars but the gas tanker does need some sort of explosion effect or even just some flames if hit hard enough. Although with the way the tanker trailer is right now it would probably just end up looking really funky when damaged.
I don't think cars should explode, but in regards to the tanker, it should be able to catch fire, and if it burns long enough, it should BLEVE. https://en.wikipedia.org/wiki/Boiling_liquid_expanding_vapor_explosion