This is horrifying. I don't know what to do then. I can get guns right now, but that's so unappealing and scary to me. At some point though, living another day is just as terrifying as dying.
Many cars have a catalytic converter so it will be impossible to kill yourself with this method.
If you still want to go ahead and use a car it is better to use the charcoal method in a sealed car or tent etc. You would have to make the car 100% airtight with strong tape along all the seals or anywhere where the air could escape.
Many people use a disposable BBQ you buy at a garage or hardware store which comes with charcoal bricks etc and metal base. You would burn the charcoal bricks outside the car until all of the smoke has escaped. Once the bricks have turned majority white and no longer smoking you would then bring it to the sealed car and give yourself at least 30 minutes for the carbon monoxide to work and fill the car.
You would then sit back and relax and eventually you will pass away.
You should also have a carbon monoxide meter that can measure the levels of co2 be released. It must be a high ppm release for this method to work effectively.
You would also need enough BBQ sets to make sure enough co2 will be released at a high level, possible at least 5kg of charcoal brickette.
Many people do this in a sealed tent in nature or in a small hotel room making sure all escape routes are blocked by tape or towels etc.
I hope this helps you to better prepare.
You can also look at the following link to read more information and get specific advice from other members.
https://sanctioned-suicide.net/threads/carbon-monoxide-megathread.2053/
Thanks