On Burning Oil

Wrapping up another flame-filled week at the Hotspot: I'll come out and say that the use of burning oil bugs me in D&D. Let's see if I can explain why.

First of all, if you look at classic D&D, the player's materials (OD&D Vol-1, or AD&D PHB, etc.) contain descriptions of offensive resources like weapons and their damage, class abilities, attack spells, etc. Then burning oil gets described in the referee's book (Vol-3, or DMG), and it's like this "secret" resource that only expert players know to call out for. It's not something out in the open for regular players to opt for. And worse, if oil turns out to be a better weapon than some other element, then it will pretty quickly replace that other element in your milieu (maybe daggers, or slings, or hold portal spells, etc.), even if you didn't foresee your gaming being about oil-slinging adventurers, or whatever.

I mean, I've had acquaintances who were D&D players in other games proudly announce, "We got giant barrels of oil and just flooded the whole dungeon and lit it on fire from the outside, and got all the XP!" I mean: That game sounds like it royally sucks, man. And it's certainly not what the D&D game "says on the tin", so-to-speak.

Secondly, but a related point: Since oil is obviously such a secondary-thought bolt-on to the system, there's not much consistency to its effect. In OD&D the effect is actually nothing except for possibly scaring off pursuing monsters: "Burning oil will deter many monsters from continuing pursuit." [Vol-3, p. 12] -- in addition to the other options of food (for dumb monsters) and treasure (for intelligent ones). Although, in its brevity I guess that allowed lots of people to interpret their own damage statistics for oil, frequently numbers that rivaled fireballs or any other mundane weapon. In AD&D, this was officially set at 2d6+1d6 (over two rounds) for a direct hit from a flask of oil. Well hot damn, that's more than any other weapon in the system, see what I mean? (Exception: tied with a heavy lance or 2-handed sword vs. large opponent.) And that's just for one flask, when your players start asking for whole barrels of the stuff, and arguing that it does 20d6 or something per barrel, and whole exploding fire-ships in your naval game, what do you do then?

Thirdly, I don't even think that it makes real-world sense that you can use a flask of oil meant for burning in a lamp, and get it to explode like Greek fire in this way. I'm no chemist, but it sounds like someone's conflating different kinds of oil in a way that's not justified. Check out the Wikipedia page on Oil:

Organic Oils

Organic oils are produced in remarkable diversity by plants, animals, and other organisms through natural metabolic processes. Lipid is the scientific term for the fatty acids, steroids and similar chemicals often found in the oils produced by living things, while oil refers to an overall mixture of chemicals. Organic oils may also contain chemicals other than lipids, including proteins, waxes and alkaloids...

Mineral oils

Crude oil, or petroleum, and its refined components, collectively termed petrochemicals, are crucial resources in the modern economy. Crude oil originates from ancient fossilized organic materials, such as zooplankton and algae, which geochemical processes convert into oil.[6] It is classified as a mineral oil because it does not have an organic origin on human timescales, but is instead obtained from rocks, underground traps, or sands; however, mineral oil by itself refers to a specific distillate of crude oil.

So it appears to me like you've got two very different kinds of substances that both happen to called "oil" due to a linguistic quirk. Which did medieval-style lamps run on? The former. ("The main fuel in Western nations was olive oil in ancient Mediterranean cultures, though extracts from fish, crude fish oil, nuts, and cheese were also used." Link.) Which does a weapon like a Molotov cocktail use? The latter. ("A Molotov cocktail is a breakable bottle containing a flammable substance such as gasoline or a napalm-like mixture and usually a source of ignition such as a burning cloth wick held in place by the bottle's stopper." Link.) Then I've also had friends start talking to me about the need to aerosol-ize the oil for weaponization, although I'm afraid that's not a claim that's within my personal area of knowledge. But clearly there's a reason why Greek fire was so special in the ancient world. ("Most modern scholars agree that the actual Greek fire was based on petroleum, either crude or refined; comparable to modern napalm..." Link.)

Therefore, I think that the next time someone asks for burning oil in one of my D&D games, my response will be: "This oil is actually olive oil for use in lamps, and it cannot burn in the open as a weapon." -- you know, quite a bit like the Gygaxian response to someone choosing to dig up some saltpeter and construct gunpowder in a D&D campaign (except perhaps better justified). Not that following real-world physics is a necessity, but more importantly because the gameplay I want is not about oil-slinging dungeoneers to the exclusion of their other weapons and spells; and as usual: real-life research solves a lot of game design problems.

Have I got the chemistry issue right? Would medieval lamp oil burn in the open like a weapon (or worse, explode)? And what's your take on the gameplay considerations?

(Photo by visionshare under CC2.)


  1. IIRC dropping a lit match into a beaker of olive oil does nothing more than put the match out. If you stick a lit match into a beaker of gasoline you'll get the same result.

    In gasoline, unless I'm very much mistaken, it is the vapour that burns and not the liquid. I imagine, but can't prove, that the same is true for organic oils.

    I think breaking oil down into two or three groups for roleplaying might be an idea. I'd go with Alchemist's Oil (minerals oils), Lamp Oil (unrefined organic oil) and Cooking Oil (refined organic oil).

    Alchemist's Oil will burn freely, and is a key ingredient in Alchemist's Fire, but Lamp and Cooking oil require a wick to burn. Although you can heat both to the point they ignite it is far harder than with Alchemist's Oil.

    Natural fire does 1d6 damage per round if you're in direct contact, 1d8 if in an enclosed space or if there is thick, choking, smoke.

  2. Distilled alcohol will also burn well, and makes for a decent molotov anddoes not seem out of the reach of medieval types. Also ambergris and spermaceli from the sperm whale (and apparently any processed whale blubber for lamp oil) are also volitile - with kerosene replacing it for lamp oil. Whale oil would be hard to get (esp inland) and not something you would want to throw at a monster (might as well throw a bag of gold at him). Alcohol of say a 151 proof variety might be a different story.

    1. There of been YouTube test of alcohol Molotov cocktails. It doesn’t work, even with the highest proof alcohol.

  3. Forgot- I would say molotovs of the alcohol or any variety would do 1d6, since swords do 1d6.

  4. Most likely they would be using the same type of pitch torchmakers were using. So flaming 'oil' and lamp oil would probably be in the same shop but not the same bottle.

  5. GURPS deals with this issue by stating that the "classic fantasy" oil flask is an earthenware jug of Greek fire (naphtha mixed with saltpeter and tar or fat) with a burning wick attached, and treats it identically to a Molotov cocktail. This fits in with the hand-hurled naphtha bombs used during the Crusades. GURPS also discusses the "notorious unreliability" of such devices, and makes the chance of failure (the wick separates in flight or goes out, or the fuel simply fails to ignite, or whatever) pretty high, about 37% (unmodified 12+ on the 3d6 "to hit" roll).

  6. I agree that it is unrealistic and abused, but I do like leaving it in the game as a resource for low level M-Us who are out of spells (their terrible to-hit helps make it a weapon of last resort), especially if you're not doing AD&D with rapid fire darts. It also gives low-magic parties a chance against a lot of foes that are not so vulrnerable to swords.

    But barrels of oil flooding a dungeon -- and yielding XP!! -- no way.

    I made 'weaponized' oil more expensive but available. The palyers lose interest in after about 3rd or 4th level...by then they have more options.

  7. I'm pretty generous with my flaming oil rules, but bad to-hit roles can set fellow party members on fire. I like the fact that oil allows the PCs take on more powerful foes than they can with conventional weapons. It lures them into false confidence so I can kill them with fireproof monsters.

  8. Of Pedantry covered this quite nicely.

    I'd say allow low flashpoint mineral oils if you like but make them expensive and dangerous to carry. There are good reasons nobody carries explosives around in enormous tuns.

    High-proof distilling is not so easy either - historically there's very little alcohol over something like 30 percent before the 1700s. PC alchemists can have fun blowing themselves up trying to produce it. Alcohol molotovs generate less heat - they're a good shock weapon and might set fire to other stuff, but there's no reason to allow massacres from vats of the stuff.

    But in the end there's nothing wrong with DM fiat when it comes to designing the world. You don't want petrol, you can say there's no petrol.

  9. I've cracked down on oil use in my games over the years. You can't make a molotov that will "explode" but a lit flask or lamp chucked at something will spill or break, spreading burning oil over the surface. Also a flask of oil doesn't make that big a pool or burn very high. It's fire, so a dumb animal chasing you might get scared, but it's not a Wall of Fire.

    Ever see "Silverado"? Remember the scene when the bad guy chucks the lamp at the books on the wall? That's about what an oil flask would do. It'll get something flammable burning quicker, but it don't go BOOM!

    Chucking a lit flask at an opponent is iffy in my games. A hit means the oil splashed on him and caught, but one round of dousing or stop/drop/roll ends the damage. A miss means you might light something or someone you didn't mean to.

  10. ...OK, scratch the comment about alcoholic strength and dates - I'm not sure of my data, sorry. Still, think of the quantities involved: a metric ton (not far from a Dutch cornlast or 2 standard 17th century tuns) is a cubic meter of fluid - that's about 35 cubic feet, or enough to run say 150' down a 10' wide corridor before it just soaks into the ground. Moving those 2 tuns is going to take a cart and a donkey, over easy roads, and it's going to cost a fortune, partly because there's almost certainly no industrial alcohol market, so it will have been made for drinking, assuming there's a working distillery trade and all that.

    That said, Willem Bontekoe's ships was quite handily blown up by a candle falling into a brandy vat - in an enclosed, poorly-ventilated space in the tropics, so it was presumably nice and warm already. And even then the brandy alone burned for a while and went out. The problem was that they were carrying coal under the barrels, and gunpowder next to the coal.

  11. In my Thracian Hexcrawl the players have started calling them "Thalmain Cocktails" after a halfling that managed to single-handedly hold off a dozen lizardmen at a chokepoint using hurled flasks of oil to keep a prepared oil field fueled.

    I think an almost self-evident case can be made that lamp oil doesn't make for a reliable offensive weapon. But, with that being said, I think taking burning oil completely off the table removes a valuable and distinct tactical resource.

    But I also don't think there's anything so special about burning oil that it should be allowed to outclass every other weapon. OD&D's maxim of "all attacks deal 1d6 points of damage" is a pretty good one to follow.

    I'd suggest drawing a distinction between:

    Lamp Oil: For burning in lamps. Might be useful for dousing flammable material to make them burn faster, but in general this isn't going to be useful for any sort of combat utility.

    Combat Oil: Primarily useful for creating a "zone of fire". Creatures passing through the zone will suffer 1d6 points of damage. Can also be hurled as a splash weapon, but will generally only deal 1d6 points of damage to a target before it's assumed they put it out.

    Alchemist's Fire: An expensive, sticky combat oil or "Thalmain Cocktail". Generally won't create a "zone of fire", but is very good at sticking to an individual target -- lighting them on fire for 1d3 rounds and dealing 1d6 per round. (They can take extraordinary action to put it out early.)

    This is pretty similar to what I did for Legends & Labyrinths using the hazards system.

  12. @richard- I would allow distilled alcohol in a flask or container as a molotov but carting around large ammounts in an effort to exterminate dungeon denizins wouldn't work due to the fact not thant much can be produced and the operation of getting modern production ammounts down a hole would probably be disrupted by the inhabitants of said hole. Given that distillation is a known technology in the 1200's and a guarded one prior to that it makes sense that this would be available in a place where you can buy chain or platemail. Flask ammounts, ok. Barrels, ok. The annual output of the Smirnoff Distillery, no.

    From Wikipedia:
    Clear evidence of the distillation of alcohol comes from the School of Salerno in the 12th century. Fractional distillation was developed by Tadeo Alderotti in the 13th century.

    In 1500, German alchemist Hieronymus Braunschweig published Liber de arte destillandi (The Book of the Art of Distillation) the first book solely dedicated to the subject of distillation, followed in 1512 by a much expanded version. In 1651, John French published The Art of Distillation the first major English compendium of practice, though it has been claimed that much of it derives from Braunschweig's work. This includes diagrams with people in them showing the industrial rather than bench scale of the operation.

    Liquor that contains 40% ABV (80 US proof) will catch fire if heated to about 79 °F (26 °C) and if an ignition source is applied to it. (This is called its flash point. The flash point of pure alcohol is 62.88 °F (17.16 °C), less than average room temperature.)

    The flash points of alcohol concentrations from 10% ABV to 96% ABV are shown below:
    10% — 120 °F (49 °C) — wine
    20% — 97 °F (36 °C) — fortified wine
    30% — 84 °F (29 °C)
    40% — 79 °F (26 °C) — typical whisky, brandy
    50% — 75 °F (24 °C) — strong whisky
    60% — 72 °F (22 °C)
    70% — 70 °F (21 °C) — absinthe
    80% — 68 °F (20 °C)
    90% — 63 °F (17 °C) — neutral grain spirit
    96% — 63 °F (17 °C)

    Beverages that have a low concentration of alcohol will burn if sufficiently heated and an ignition source (such as an electric spark or a match) is applied to them. For example, the flash point of ordinary wine containing 12.5% alcohol is about 125 °F (52 °C).

  13. Also given that the fire would burn clear in regular light and blue in the dark it would have a name like clearfire or bluefire.

    Verification: abbywar

  14. Also it seems to reason that if you can get enough fammable fluid into a dungeon to burn the ENTIRE dungeon you have probably already drowned the inhabitants and you might as well have just used water. The said operation again being fairly impractical.

  15. Arrggh!! I keep thinking of stuff. Also note that alcohol had a lot of common pre-industrial medicinal uses, and so would be in the healers tools in some form. It makes sense that adventurers would be wandering around with this stuff: 1) for the obvuious molotov reason discused here 2) for cleaning wounds 3) for getting snockkered when they get all that gold back to town!

  16. Oil doesn't explode, but even non-exploding oils are dangerous when they catch fire. Cooking oil is a source of grease fires, which can set fire to your kitchen or clothes. I'd give a 1 in 6 chance of other flammable material catching fire when exposed to fire.

    Otherwise, oil that's on fire causes 1d6 damage to anything engulfed in it (same damage as any other non-magic or non-giant weapon) and keeps doing damage as long as a victim takes no action to counteract, like rolling on the ground. More oil doesn't do more damage, it just covers more area. The trick of pouring barrels of oil down a flight of stairs wouldn't work (it might create an impassible zone for 1 turn and alert dungeon occupants, but presumably creatures in a non-flammable stone dwelling are just going to avoid the flames.)

    Even if it did kill all the creatures on a level, you get experience points for actual experiences. Avoiding experiences doesn't net you any experience points.

  17. I'm with Talysman; breakable flasks of decently refined common oil with burning wicks (more safely tied around the bottle rather than stuffed in the neck) seem like a workable weapon, but more as a potential anti-structural and panic-inducing tactic. 1d6 damage per round, with misses going out, sounds pretty reasonable, especially with a chance of fumbling and setting oneself on fire.

    I'd be more interested in rules for using fire in sieges and against ships, and once given those uses it seems inevitable that players will want to apply them to small combats on occasion.

  18. Also, GMs can defeat the barrels of oil tactic by making most of the treasure tapestries, incense, gemstones, and magic scrolls.

  19. Wow, awesome bunch of comments! Richard: Thanks enormously for the Of Pedantry link, a great and convincing writeup.

    I'll say this: I can see the attraction to adding a "Greek Fire" substance to the game (at special expense and risk) -- but that it pretty much simply cannot be the "flask of oil" listed in the basic D&D equipment list for 2gp. Mostly agree? (Now that I think of it, compare to Gygax's oil of fiery burning in the UA -- same basic effect, value 4,000 gp!!)

    For simplicity in my own game, I do plan on just saying that petrol-based weapons are not available.

    One thing that no one else has touched on -- Are you offended in any way by having this super-weapon "secretly" hidden off-book for the (new) players? That kind of thing smacks me as really stinky cheese.

  20. One other thing: Per Gygax, "... when gunpowder is brought into the fantasy world it becomes inert junk -- ergo, no clever alchemist can duplicate it. Likewise, dynamite and similar explosives become inert." [DMG p. 113]

    So one might argue that it's even more inconsistent with all the related "inert junk... similar explosives" in the baseline D&D fantasy world.

  21. Any raging inferno of sufficient power to kill the inhabitants of a dungeon, should be sufficient to have opened a portal to the elemental plane of fire/hell and the GM should convert all the monsters burned alive into undead ones made of fire.

    It's easy (and boring) to look for ways to tell the players, "No, you can't do that." better to say yes and have fun with the consequences.

  22. I agree with Delta on the matter of stinky cheese.

    Both stinky cheese and flaming oil are going on my long-form equipment list with a usage note for each. ;-)

    Skimming around for research info, whale oil looks like it still has a very high flash point at 400 F (http://mysite.du.edu/~jcalvert/railway/railamps.htm), comparable to the low-end of vegetable oils.

    After absorbing the pedantry and other information, I'm thinking if it works as a weapon doing damage in personal combat, we're talking about naphtha or some alchemical compound.

    What remains?

    Lamp oil Molotov cocktails might work for small structure fires, but probably less good than pitch torches.

    Fire pots with flaming coals are probably better siege weapons for use against castles, let alone just building a pyre against (or under) the walls.

    Hot oil works as a defensive siege weapon. Heated to near-boiling, it becomes flammable, should the targets survive having the liquid poured on them. Of course, you might set your own defenses on fire...

    That being said, I'm still not opposed to a reasonably-priced (at the cost of a bundle of arrows) weapon that does damage proximate to that of other weapons (1d6, per round) and has comparable chances to hit. The advantage of fire weapons is the ability to create panic and distract opponents from fighting, which I would balance against the need to spend an round to prep the weapon before it can be employed.

    Then again, I make holy water cheap too, so what do I know.

  23. Side note on holy water:

    I actually lean towards it being too cheap to meter, but you have to bring your own container lest you're charged the mark-up rate on bottles, and the priest may not have much available with less than a day's notice.

    The list price only really makes sense if its something like Zam Zam Water (http://en.wikipedia.org/wiki/Zam_Zam_water) that has to be imported at great expense or if the church has a major racket going. I never really like the "dissolve a pound of silver in to a pint of water" recipe that was standard as of 3.0.

    I'm curious as to what you do with holy water, Delta, especially since you don't use PC clerics.

  24. Indispensable:

  25. I always figured that flaming oil being broken was the point. That if your approach to first level in old school D&D was to make standard melee attacks every turn you were doomed to never have a character survive to second level. So the meta-game is to figure this fact out and break out of the box.

    It follows that DMs saying, no you can't do crazy scheme X, it's not heroic enough or genre-appropriate, frustrated the heck out of me. Unless you're playing a system that actually gives you a more powerful, survivable starting character it's a misplaced sentiment.

    But I am persuaded that different kinds of oil should be broken out, and lamp oil should not be the equivalent of napalm.

    And I'll concede that hiding flaming oil in the DM's section was a dick move.

  26. The Holmes Basic rules have some unique rules for oil (& holy water) that were not carried forward. I wrote up a summary here. Holmes requires that the oil is spread out before lighting, either poured on the ground, or thrown at a target. So two rolls are required, one to hit with the oil, one with a fire source. Uses a special "to hit" roll based on size that does not take AC into account.

  27. Thanks for the link and the comment guys.

    I wanted to add 2 quick pieces of pedantry for yall to muse over:

    1) Only vapors burn. Solids and liquids CANNOT burn. Liquids only 'burn' by emitting vapor and that takes you back to my blog post about flash points and vapor pressure. What is really interesting is how then does wood burn? Wood, and other solid organics, emit flammable vapors when heated. Neat stuff for a chemical engineer and associated nerds. Look up "pyrolysis" for more information on how solid materials actually burn.

    2) Some suggestions here make a distinction for oil that can be used as a bomb, being made from crude cuts of petroleum, or a concentrated distillation of alcohol. Remember one thing, if a liquid is volatile enough to be ignited at room temperature, it will also have an appreciably high vapor pressure, meaning it will evaporate. This requires a sealed, pressurized container for storage and would be very impracticable for an adventurer. Remember, there is a trade-off between volatility and stability: the easier something is to ignite (making it suitable as a weapon), the more dangerous it is to safely handle and the more work that has to be done up front to process it.

    Have fun guys!

    PS (Ok, I lied, 3 pieces of pedantry): Alcohol has a very low heat of combustion when compared to oils. This means alcohol will not burn as long nor release as much heat energy. For instance, an oil weapon made out of something that you could produce in the medieval/early modern period would give off around 20,000 BTU per lb of stuff burned; 80 proof alcohol gives off about 4,000 BTU per lb. So if burning oil in your world does 1d6 damage, maybe alcohol should only do 1d2...

  28. Anthony: Thanks for chiming in here!

    Joshua L. Lyle said: "I'm curious as to what you do with holy water, Delta, especially since you don't use PC clerics."

    That's a good question. To be frank, it hasn't come up in my game in a few years.

    Note that I do play with OD&D as my base, and there's no mention anywhere in OD&D of any tangible effect from holy water. I actually don't mind it remaining on the basic equipment list... as an expensive fraud. (Or: I suppose I could convert that particular line to the potion of healing.)

  29. It's pretty clear to me that as a group we have no idea how much damage being burned should do. It certainly hurts a lot, but compared with an axe blow? OTOH, the special thing about burning is, it keeps happening until you stop it. So it's really a game mechanical issue: it should do as much damage as you want it to, per Delta's original suggestion.

    Even 1d4 a round - until you take action to put it out - is bad news at low levels. It's a sure momentum (initiative) and morale killer. That makes it a great anti-goblinoid weapon, without the need for out-of-scale damage dice.

    And putting it in the DMG was moldy, but I don't recall EGG's wording: isn't it possible that it's just bad organization?

  30. Here's a really quick heuristic for burning damage off of the top of my head:

    All fire damage, regardless of source, does ascending damage. Meaning, 1 on the first round, 2 on the 2nd, 4 on the 3rd, etc. Basically, 2^n where n is the number of rounds burning (start at 0). The difference between fire sources could be how easy they are to extinguish. So a Greek Fire-like substance made from petroleum products wouldn't go out nearly as easily as an alcohol based weapon. And the more effort and people put to work extinguishing a fire, the less damage it does. Makes for a great weapon to control the battlefield.

    Just a thought...

  31. About burns- there are generally 2 categories of burn victim: Those that will die from their burn without medical treatment, and those that won't.
    @Anthony- you don't need that many BTU's to burn up a person in 6 - 10 seconds. Splashing someone with a liter of 151 and setting them on fire is going to f--- them up. Even before they stop drop and roll. So a bottle of 151 with a flaming rag tied to it is bad news. And will do some damage (severe burns) before the stop drop and roll gets rid of the flames. The average joe has 1d6 hit points. The average 750ml bottle of lit 151 can do enough damage to threaten a life PDQ.

    I would never stop my players from trying anything. That is the pleasure of DMing.

    Here is some info on burns and how the American Burn Association classifies them for referal to a general hospital or a special burn unit. The rest of the article is useful too.


  32. How big is a "flask" of oil in OD&D, anyway? As big as a medicine vial? Coke-can sized? I can't even find anything in the LBBs about how long 1 flask lasts.

    I appreciate the point in the Pedantry link about "natural laws", but, then again, it says specifically in OD&D (Vol. 3, p. 24) that you shouldn't let "real world" laws define your campaign. It's perfectly possible what they use in OD&D-world for "lamp oil" has nothing to do with what real-world medieval societies used, and thus might well be closer to unrefined petroleum or something like that.

    That said, while I agree fully that burning oil is a valuable resource for low-level delvers, the idea of burning out a whole dungeon with it or doing 20d6 or anything like that is just STOOPID. Yeah, guys, c'mon over and try to burn out my dungeon - which will just happen to be full of fire elementals, fire toads, azers, iron golems, flame snakes, salamanders, efreeti, fire giants, magmen, lava mephits and red dragons. OOPS.

  33. Pere Ubu said: "How big is a 'flask' of oil in OD&D, anyway?"

    Right, that's one of those things you have to turn to AD&D for any specification. PHB p. 102 says lantern burning time is 24 turns, "from 1 pot (pint) of fine oil".

    And again I think if anything the fantasy-world precedent for this stuff is to be LESS volatile than in the real world. DMG p. 113 "inert junk" explosives and all that.

  34. The main problem with flaming oil is that you need one action that hits to cover the target and another action that hits to throw a flame on it. You need a pre-lit flame, not a flint and steel in the middle of combat, so it means breaking your lantern or tossing a lit torch at him.

    Side note: Fire Trap spell cast upon a treasure chest. You break the treasure chest. Fire Trap goes off right? We always agreed that it worked in that way. So if you Fire Trap your oil flask and throw it and it breaks, the Fire Trap goes off and lights your oil. At one point I as a player had a Cleric with a bunch of these, and fell into a pit, and failed some important item saves. Ended up rolling a Thief or something after that ;P

    2E D&D made a distinction between lamp oil (6 cp per flask) and Greek Fire oil (10 GP per flask). I think the extra cost for Greek Fire was so high that nobody would be able to afford to throw a barrel of it at an enemy.

    I'd also have the barrel make its item save, and count it as Thick Wood since it has metal bands etc. The greek fire, as a sticky mess, would spread out but not like water. So if you had thrown the barrel at a Giant and the barrel shattered, it wouldn't deliver the entire barrel's contents upon the Giant. And because it doesn't flow as smoothly as water, you could dump 10 barrels of 250 flasks per barrel into a dungeon and see it only flow 200' in. If your dungeon level is 30x30 10' squares, 20 squares of flow is nothing and while it might fry a couple monsters it isn't going to be that many, certainly not the whole dungeon. It also burns up a lot of treasure, and cost 25,000 GP to accomplish not counting transportation costs. That assumes there is even 2,500 flasks of Greek Fire to be had at once. On the other hand, the air in the dungeon might be exhausted because of the burning oil. While that might drive monsters out of the area or even kill them, it would also make exploring the dungeon later very difficult.

    You could also reduce the oil damage, perhaps to 1d3 per round for 4 rounds. It turns the oil into an area-denying weapon and of special use against spellcasters, preventing them from casting. I'd include a rule that immersion in water gives minimum damage on any immersed round and that "stop drop and roll" gives -1 damage each round of rolling prone.

    Finally, would they get the monster EXP for burning out a dungeon? What if you sneezed on a monster and gave it a disease, from which it later died? What if you, re-shingling your house, slipped and let a slate tile fall to the street far below and decapitated some 0-level beggar? Do you get the 7 EXP he's worth? I'd say at best the PCs would get half EXP value of monsters killed in such an indirect action, but that would be generous.

  35. 1d30 -- Interesting observation that the 2E PHB had "Greek fire" as a separate and somewhat pricier item.

    Again, I also think it's an interesting case that in Gygax's UA he had an "Oil of Fiery Burning" item that did 5d6 damage in 1", cost: 4,000 gp.

  36. This is a non-issue. 5e D&D has it very clear: Lamp oil can be splashed onto a target, which makes it take 5 extra points of fire damage every time it takes damage for the rest of the combat. It doesn't ignite the target; it doesn't do damage over time. It can be poured onto the ground, in which case it does 5 damage to anyone that ends their turn or enters in a burning square. Again, does not do damage over time. This is organic oil.

    The other kind is called Alchemist's Fire. This causes 1d4 fire damage over time. The only way to save is by spending an action to do a DEX save and douse the flames.

    1. Well, that's still too much and doesn't make sense chemically. Also: Vegetable oil contributes more damage than alchemist's fire? Ugh.

  37. In this summer's home-brew, I'm likely to declare that flaming oil is white naphtha/kerosene , pretty much), distilled by Dwarfs and human alchemists. Fun, possibly irrelevant real world historical note: the Chinese were distilling mineral oil for use in illumination long before it became common technology in the West. They also made some use of natural gas for gaslight.

    1. That's a cool historical tie-in! I always like dwarves being given some slightly anachronistic technology level.

      Side note: At one point I tested trying to light a puddle of kerosene on fire, and I couldn't get that to work, either. Link.