Plumbing issue. Odd substance backing up in garage floor drain.?

There should NOT be a FLOOR DRAIN in a garage, that is connected to a SANITARY or STORM DRAIN main.

The usual use by the ignorant is to drain their engine oil into it. It's simply not allowed.

Find out what system (if any) your floor drain is connected to.

If it simply goes beyond the walls of the garage and dumps onto the grass, it would make the most sense. But it surely wouldn't/couldn't back up.

In a place with winter snow, it could melt and drip onto the garage floor and be routed outside. Beyond that, it's surely not allowed, due to the possible misuse by the ignorant.

snake it

It may be connected to a soakaway which is clogging up and backflowing. I doubt if it is the main sewer or it'd smell. You might care to enter into some investigation, perhaps seeing the direction it drains in and gong outside with a shovel to try to find the pipe.

Sometimes metal pipes will "sweat" - that is, warm up and evaporate water in the air, cool off and become water to collect in a puddle, then evaporate into a gas, leaving collected solids behind. If the substance has no smell and is clear, it might not be back flow or backwash from the drain. Most floor drain pipes drain into the main sewer line, or a septic tank. However, if you DO have a septic tank and recently moved in, it may be the residue of soluble gases from the septic tank that pipe drains into, the gases evaporated into steam and went back up the drain pipe through natural air, collected outside the pipe, cooled and puddled, collecting former oil residue along the pipes as the gases moved through regular air flow. (oh goodness me, this is sounding like "wet farts", dang it.) But, really, if the septic tank was cleaned out before you moved in, the trapped gases and steam inside the tank are coming back up this pipe into the open air of your garage, only to cool and puddle near the opening. The water or regular H20 evaporates into the air, the soluble oil residue from the pipes that had collected for the previous 40 years are left behind after the water evaporates out. Because this happens quickly, mold and germs have no chance to form and grow in the fluid to make a smell. Because this pipe is acting as a vent for an underground issue, you may wish to install a Carbon monoxide sensor and alarm system in this room to measure carbon monoxide collection along the ceiling of the garage. If the garage door opens and lets fresh air in, the carbon monoxide might not build up heavy, but if the doors stay shut all through sever cold weather, having a Carbon monoxide alert in this room may be a suggestion. This is just a theory, but, good luck with finding out the real source. Do get someone to measure the gases around the pipe opening, if possible. A professional can tell you for sure what this liquid is and if it is dangerous to you.

i dint kno

It sounds like water from the clothes washer. Call a Plumber.

Maybe someone dumped motor oil in there. Wherever it drains into what? Sounds like the chances are it does not drain correctly. It probably needs a snaking .
Or maybe it is just a pit. You need some how to pump it out. Is there a sump pump there?

This summer when it is dry, fill the drain line up with water and start looking for a drain line and exit to someplace. You should find a wet spot if you put enough water into the drain, and it drains. You might also pour a bottle of drain cleaner in it just to unclog things . My guess is that it is a drain line for washing the garage floor, and the line drains outside and dumps in a nearby swale. The end of the drain is grown over with vegetation and is line is now mostly plugged and water backs up from rains.

With no smell, it's not likely to be connected to your sanitary sewer line. I might guess that it's plumbed to a dry well, or cistern of some kind, which has become contaminated.

Any chance your home had an underground fuel oil tank in the past?

Call a plumber.

There will be a P trap under the drain. It's full of disease. Remove the cover grill, Take the garden house and wrap a rag around it big enough to fill the hole and stuff it in the drain, hose and rag. Stand on it while someone else turns the hose faucet on full and blow the drain out.