Originally Posted by SilverSaint
There actually are specific rules for throwing oil on the ground and setting it on fire. It deals a straight 5 fire damage to a creature that enters or ends its turn in the fire, and burns for 2 turns. It doesen't set you on fire or anything.

You can also throw the oil at a target, covering them instead of the ground. You just have to hit them with a range attack w/an improvised weapon.
Originally Posted by CMF
So per the case of fire dmg in game (1-4 dmg per turn) and fire dmg on tabletop (5 dmg static? per turn) it is consistent?

If you throw oil at a target and then set it on fire (firebolt=1d10 damage), that is 2 actions for 15.5 damage (5 "on fire" damage for 2 turns, 5.5 for firebolt)
If you throw oil at the ground and then set it on fire, that is 2 actions for 5 damage (assuming the enemy stays in the pool of oil), but you get a bit of battlefield control.

In BG3, you can cast firebolt at a target which sets them *and* the ground on fire. They are set on fire for 2(?) turns. That is 1d6+1d4+1d4=8.5 damage for the cost of 1 action, which is comparable to 5e oil+firebolt's 15.5 damage for 2 actions. Seems fine...

But! BG3's firebolt also sets the ground on fire, and you can do this every turn. (I believe that alchemist's fire in BG3 also sets the ground on fire, whereas in 5e it only sets a single enemy on fire).
In addition, in BG3 if you miss with firebolt, you still set the ground on fire. In 5e, if you miss either the oil flask throw OR the firebolt, the enemy does not get set on fire. BG3 allows you to, in effect, cover a person *and* the ground in oil/fire at the same time for a similar action cost.

Conclusion: In BG3 it is easier to deal direct fire damage to enemies and much easier to cover the ground in fire surfaces.