Lets put things into the proper "Perspective" and assess the situation with "Common Sense & Logic"
* You can "BOMB" your car, which will probably work .... never mind the Battery Disconnect ....
* You can also "BOMB" the underside of the car in-case the 8-leged
is hiding under a guard or inside an inner-guard.
* You can also arm yourself with a High Powered LED Torch and a 4lb Hammer.
Sit Very Still, Quietly & Patiently in your car all night waiting for it to appear, and when it shows, "Kapow" .....
This method will definitely work, however, you will only get one strike to kill it.
Remember to aim precisely and don't miss, or you will end-up damaging the interior.
Come to think of it .... you'll probably damage something anyway ....
* Not so sure the Peppermint Air Freshener or Mothballs is going to work, sure they repels & possibly kills Ants.
But it wont bother a Big Hairy
from coming out to feast on a meal of Dead Juicy Ants ... 
* Spraying every Nook & Cranny with an Extension Tube attached to a can of Pesticide .....
Comon .... have you really got the time to be pissing around doing that .... beside: what will the neighbors think your upto.
* A small Thermo Nuclear Weapon is out of the question ...
The only Black Markets where you could purchase such weapons have been eliminated: Sadam Hussein, Gaddafi, Bin Laden.
* Two Bricks ...
Well .... what else would expect from a Queenslander ....
..... with sore Thumbs ... 
As I said in the Beginning ...... "Common Sense & Logic"
Your dealing with and Creature that eats other Creatures for Survival .....
You need to Introduce a Natural Enemy ...
"UNQUESTIONABLE SOLUTION"
1 - Take a Breeding pair of Native Lizards and let them loose inside your car.
Once they begin to breed they will decimate the entire spider population.
2 - Find a Snake species that eats the Lizards.
They should not take longer than (3) days to eat the Lizards, since they don't eat often.
3 - Weasels eat Snakes. Any old Weasel should do, but a Mongoose would be much better.
4 - Coyotes or large Cats eg:Panthers / Cougars love to hunt and kill Weasels / Mongooses.
CAUTION: Do not introduce Large Cats in the presence of Young Children, tell the neighbors to lock-up the kids inside first.
Finally: A Brown Bear.
Bears really have no natural enemies so you will either have to contract the local Police with a shotgun or let the thing starve to death.
Appropriately, you should exercise Safety and allow the Bear to Hibernate before calling the Police with a Shotgun.
Good luck with you Spiders ....
And remember to post-up when your done ....
Sam ......
.... It went from Bad to worse 
Nice Try Though ...you gave me a laugh 
just a spider nest casually in my drivers side mirror.
Awesomeness Augmented
