Let's look at the legality of Teargas first. And I am going to go Hard with you and drag you to the worst courts:
If you are in the military, then you can't possess it at all legally as that alone would break the Chemical Weapon Convention - and using it against civilians, even protesting ones rocking your car would break all kinds of laws. Nope, your car is armed with an illegal substance (fr the military) as an irritant is counted as a chemical weapon for the military, so you can NOT use it, and you might end in front of a military tribunal for its use or, in another country, in Den Hague as a war criminal if you use it. If you are a civilian of a PMC in a warzone, you might get charged as an illegal combatant above that!
Let's put you to New York... and you are in hot water, because your device is not pocket sized, making the dispersion mechanism illegal and thus your use of it use of an illegal weapon:
PEN § 265.20 14. (a) As used in this section “self-defense spray device” shall mean a pocket sized spray device
Let's go to California. You may have your tear gas car there, but you might not be able to use it as you wanted... because to be able to act in self-defense you need to be
The defendant reasonably believed that (he/she/ [or] someoneelse/[or] [insert name or description of third party])was in imminent danger of being killed or suffering great bodily injury [or was in imminent danger of being(raped/maimed/robbed/ [insert other forcible and atrocious crime])];
The defendant reasonably believed that the immediate use of deadly force was necessary to defend against that danger;
- The defendant used no more force than was reasonably necessary to defend against that danger. CALCRIM No.505
You'd need to prove "imminent danger of being killed or suffering great bodily injury" - you are sitting in a car and the car gets pushed up and down - because if your car has a defense system of that caliber, your car is most likely armored and nothing but its paint job is in danger but for an RPG or blowtorch. The crowd might make you anxious, but it does not put you at danger, nobody has pulled out a handgun to even attempt to threaten you (and possibly ricochet into the crowd), nobody has pulled out a baseball bat to hammer upon your car. The crowd does not really provide a threat to you but for the vehicle, and even worse, the situation was brought to be this by the action of OP who riled up the crowd. And as we are not at homicide, we must look at self defense in what is the closest.. and I think that might be self-defense in combat. But, oh shock, OP did start the fight, and he did not in good faith stopped fighting and expressed so verbally and by conduct in a way that a reasonable person would understand that he wanted to stop fighting.
A person who (engages in mutual combat/ [or who] starts a ﬁght) has a right to self-defense only if:
(He/She) actually and in good faith tried to stop ﬁghting;[AND]
(He/She) indicated, by word or by conduct, to (his/her) opponent, in a way that a reasonable person would understand, that (he/she) wanted to stop ﬁghting and that (he/she) had stopped ﬁghting(;/.) CALCRIM No.3471
The second prong was given up by OP, so he did not regain the right of self defense: he lacked proper expression of their retreat from the fight he started to the people he incited. So he does not have the right of self-defense, even worse, he could be charged for inciting a riot as OP "urged others to commit acts of force or violence" against him "at a time and place and under circumstances that produced a clear, present, and immediate danger" of riot and creating danger for him - the third prong of OP intending to cause a riot would be the hardest leg to prove for the state.