Freeze effects put out the fire, but they can be reignited by other burning Oilers nearby (or the burning oil-slicks they trail, which are NOT affected by freezing effects). They run at juuuust about the same speed you do, and the healing effect only happens when they first get ignited (and again if the fire goes out and they're re-ignited). You can shield-push them or swat them away with a charged attack if you're careful. They're really greasy (what with being made of oil), so they recoil a good ways when attacked or shield-shoved.

You just have to try your hardest to clear them out without igniting them. Thankfuly they're pretty wimpy when they're not on fire. I think the ones in Tier 3 and danger rooms in the second half of Tier 2 might be able to ignite THEMSELVES-- so watch out.

...Just wait until you meet the Tier 3 Quicksilvers. It will be funny the first time, but then it's just increasingly more and more frustrating after that.

As Gigafreak already explained, freeze is they key.

One person in the party with a shivermist buster will generally make these guys pretty simple to deal with.

Just be sure to avoid your flaming teammates, and smack the one who runs over the slicks while on fire.

I hate how the color of the slicks is the EXACT same color as the oilers, so when u get a room full of the blobbing down oil slicks they become near invisible, it's ridiculous. Then you have mr.death-a-minute yank a fire vial above his head and u know the fan is about to be hit. Boooo

The best part is when someone trolls everyone with a searing edge or a fang of Vog

Flame puppies light them on fire, and firoknights, but that's only a concern in the flamelash arenas, not fire danger rooms, but it's a similar challenge. In danger rooms, just kill the oilers first before any other jellies, and if you catch on fire stay shielded and stay away from oil slicks. Whatever you do, don't blow up the red blast cube while the room is full of oil slicks! I'm pretty sure those red blast cubes set the jellies on fire (although not the slicks directly but once you have a burning jelly that hardly matters.)

Cryotech alchemers help a little (if you stop it early or get down to one or two to put out) and freeze bombs help a lot.

If you understand how the fire spreads, you can try to keep the burning ones chasing you in one corner of the room and not set the whole room on fire, and you can learn to look for paths through the oil slicks (although once the fire starts spreading through them, you better -remember- the path, because you can't see it anymore really.)

It is a challenge, but a beatable one. Quicksilvers that can shock themselves I'm not so sure about, unless you're very lucky and get lots more waves of jelly cubes than of quicksilvers in a given danger room.

But won't T3 oilers self-ignite? And if it's a 14 (or 15?) + danger room won't you fight t3 mobs even though it's a danger room in t2? This is what i think they are experiencing. Also bomb cubes will ignite oilers on explosion, as will pyro gremlins, i believe gremlin bombers as well (not sure). I've heard all of these from other players, and it seems plausible given it's hard to pinpoint when they are ignited...just Whooooooooosh, and then there is fire everywhere, hitting monster tics and melting shields.

Oh, so it's just Quicksilvers that self-charge?

...Hate Quicksilvers. So much.

Thanks, i appreciate the correction.
It's really hard to pinpoint the reason a room went up in flames after the fact (considering no one ever says, oh i did that). I think what maybe has led to some of my parties confusion then could be gremlin bombers/oiler attacks/bomb cubes pushing people into fire grates and then us stepping on oil/mob. Throw in a lil lag and we're often left wondering what just happened lol.

The Quicksilvers heal themselves and become invulnerable while charged.

Bumping into other Quicksilvers heals and charges THAT one too.

...Hate. So. Much.