This costs 3 resources, a card and 4 actions to heal up to 6 (compared with 1 less resource to heal 3 with First Aid). It has 2 limitations, however: it can only be used once per turn, and only after an enemy was defeated. The top contender for this is William Yorick, especially with Aquinnah since each horror healed is worth an extra damage reversal. Insanity prone ’s like Roland Banks may also be interested.
Uses (3 supplies). If Kerosene has no supplies, discard it.
If an enemy was defeated at this location this round, exhaust Kerosene and spend 1 supply: Heal up to 2 horror from among investigators and Ally assets at your location.
Budget First Aid.
At 3 resources and 1 Xp, you're effectively trading 1 resource and conditional triggering for a 2xp discount and monotyped flexible horror healing, which is far more useful then a damage/horror healing blend that can only hit one thing at a time.
Being limited to trigger right after someone gets a kill is tricky, it's pretty much unusable solo because of all the turns where you wont be left with a free action after a kill. Admittedly though, if you can kill something with action 1, and trigger it twice with actions 2 and 3, it'll completely turn around a bad horror situation. In duo it's a little easier, but requires you have a friend that somewhat routinely kills things, this card comes online in 3-4 player where at least one other person is usually also killing stuff and you can move in and capitalize.
Carolyn Fern doesn't dislike this card, although it faces stiff opposition for slots with Clarity of Mind and First Aid. For everyone else I say pass this by unless you have friends around or have severe horror trauma, in which case spending 1 XP for Thermos is probably every bit as good or better.