Pro-euthanasia group EXIT Australia measured carbon monoxide fumes produced by both new and old cars.
Only one Japanese model failed, producing less than the lethal dose of 1,000 parts per million of the deadly gas.
“People said this is macabre,” EXIT Australia coordinator John Edge told Reuters.
“You get the feeling it’s a lot of people around there wanting to take their life. It’s not about that at all,” he said.
EXIT Australia was set up by Dr Philip Nitschke, who shot to infamy after he helped four people commit suicide in the country’s Northern Territory region in 1997, where euthanasia was briefly legal.
The test was not to determine which car was best to die with but rather to tell EXIT members whether their cars would kill them should they decide to commit suicide, Edge told Reuters.
Euthanasia is illegal in Australia and the group is under investigation for the death of one of its members last year.
Nancy Crook, who was suffering from bowel cancer, took her life last May.