Can I hang this in my car or does it need to sit in a cup holder?

Either works. The soda-can design fits standard cup holders, but you can also vent-clip or hang it if you prefer. Just make sure it's positioned where airflow can carry the scent through the cabin.

How long does one 145G can last?

Lifespan depends on cabin size, ventilation, and how warm it gets. Daily drivers typically see 2–4 weeks of noticeable scent before you'll want a refill.

Will this stain or damage my dashboard or upholstery?

Keep it away from direct contact with leather, vinyl, or fabric in high heat. The can itself doesn't leak under normal conditions, but placement matters — use a cup holder or secure mount to avoid spills.