Whats the worst looking fluid you've drained from a vehicle?

[Rhymingmechanic]

Brake flush on a 14-year-old Saturn. I was going to say the fluid from the rear cylinders looked like chocolate milk, but the word in my notes is "caramel."

Second place was 30k mile WS trans fluid from a Pontiac Vibe. It was the color of used motor oil with a creamy metallic swirl. Blackstone said aluminum was high, but it went steadily down with regular WS and then Maxlife pan drains. Trans was fine until insurance totaled it over a parking lot wreck 100k later.

 

[IcarusLSC]

I remember decades ago when my grandmother gave me her car (my first car, a '79 Marquis Brougham with a 351W.)
It had sat for about 2-3yrs in her driveway with nothing at all done to it. When I got it first thing I did was change all the fluids which were surprisingly good except for the diff fluid, which was sludge! It was like thick tar, I dunno how there couldn't have been any damage from it, but I cleaned it out real good and put new fluid in 2x that summer and it never made noise or had any issues!

 

[zrxkawboy]

Many times ATF will be black as tar when drained out of a transfer case.

 

[Duffyjr]

Hands down for me was the gear oil out of a 1970ish Evinrude 75 hp. The worst part was the smell, I honestly started gaging.

 

[DGXR]

Had a 1992 Thunderbird back in my drinking days and I "forgot" to change the oil. It didn't have a maintenance reminder so it wasn't my fault, right? I'd check the level occasionally but it didn't burn or leak so I didn't worry too much about it. (Most other things got the same level of neglect and I was not biased against this car.) Got busy /distracted with other stuff for months at a time, then one day the topic came up and I realized I was WAY overdue, like a full year overdue. The car still ran fine I guess, but I tell you hwat... that oil was black. I mean black black, and noticeably thicker than engine oil should be. It was a good car and I felt terrible about that so never did it again. Heck I used to feel terrible for no particular reason LOL. Now sober for years, I take really good care of all my vehicles but I'm not quite OCD about it... kinda borderline I guess.

 

[eljefino]

The antifreeze from a project saturn with cracked head. It had emulsified oil in it, and the rubber hoses for the radiator "soaked up" oil that kept appearing, flush after flush. Ran cascade through everything, removed the surge tank, put some nuts, bolts, water, and cascade in that, shook it all up...

 

[4WD]

Bought a 2005 GMC 4WD with 59k … clean unit …
Well … glove box full of 3k Shell oil changes … but fluid from rear end was nasty …

 

[HyundaiAbuser]

I forgot to mention one of mine, when I had bought a b4000 with a burnt transmission i went to figure out how that had happened. What i discovered was an internally leaking radiator that mixed the old crusty black fluid with the coolant and drained both of those along with replaced the radiator. The result afterwards was a relatively good working truck for the next year and a half barring things that I did to break it.

 

[Joe1]

1986 US Army. I arrived at a new unit and did a PMCS on a CUCV Chevy Blazer with a 6.2 liter diesel engine. 29k miles on the odometer. It still had the original OEM blue AC Delco oil filter. l opened the drain plug and nothing but lumpy sludge drained out. Never seen anything like it in my life.
I poured in some fresh oil from Olive drab green oil cans and replaced the blue AC delco filter with a cool looking OD green filter. I was assigned a different vehicle shortly after, but this one
was still running when l left the service a year later.

 

[doublebase]

Dexcool 2000-2005 (any GM with over 100,000 miles).

 

[wildcatgoal]

I'm going to have to say... the blood of my enemies.

 

[Deamos]

Supercharger oil from my 2002 Grand Prix GTP.

I bought it with something like 75-80k miles and had read (somewhere) about changing the pulley lubricant, along with a warning to be very, very careful about getting any of it on my skin or clothing due to the likely reeking stench that would be encountered.

I can honestly say that the writeups I had read at the time were probably understated if anything on how bad the stuff coming out of the supercharger would stink.

It was a nice late spring/early summer day with a good breeze and *it still* stunk enough that I wanted nothing to do with what I pulled out of there. It was also this poo brown color. Given the new stuff in the two little squeeze bottles was clear and had no noticeable scent, yeah. The next time I changed it (I think I opted to do so after another 30k) it still smelled, but not nearly as bad and it was mostly clear still.

 

[cos]

A very poorly maintained Mid 80s Toyota Tercel - the coolant was probably factory fill and was about eight yrs old when I drained it. It was nasty brown water with surprisingly big chunks of rust. I flushed the hell out of the cooling system and put in a new radiator.

 

[hank2]

I can think of a number of competitors. One of the worst was the factory fill Dexron II ATF in the A833 manual trans on my '82 D150. I had changed all fluids about 3 years ago. Mileage at the time was about 170k. Black water is how I would describe it. Synchro's were pretty shot. Filled with 75W90, which was fine per FSM. The 80W140 rear diff gear oil was a treat as well.

 

[bdcardinal]

Back when I was an apprentice in the shop here we had a California Highway Patrol Crown Vic with no forward gears. Got it on the lift and dropped the pan and it smelled like old gear oil. The fluid came out black and had the consistency of used diesel oil. Thankfully we didn't need to do a teardown on that one and were able to order a black box reman.

 

[wtd]

The front diff oil on my 1998 Chevrolet K1500 truck the first time I changed it. It was milky white and looked horrible. I didn't use the 4x4 much prior to that change and I guess it was condensation buildup since I had never run the truck through any water up to that point.

The second worst was the rear diff fluid in my 2014 Mustang GT when I replaced it at around 3,500 miles to install a Ford Performance aluminum finned diff cover. It was grey in color and had a lot of sparkles in it. I guess it was all from break in.

 

[BrianF]

The dark brown, worn out, unknown ATF from my 1993 C1500. The 4L60E was shuddering when lugged and I could not pass anyone on the highway unless I babied it with the torque converter locked. Otherwise she slipped something fierce. The fluid did not smell burnt though.

I did a fluid exchange and replaced it with cheap generic Dex 3. No filter change and she shifts almost like new.

 

[ripcord]

I once had to try to clean an old diesel fuel tank that had some kind of microbial/fungus/algae habitat thing going on it. It smelled so bad and the inches thick layer of sludge in it had this melted plastic/bondo/peanut butter consistency. I've also had some nasty differentials, like from 40's and 50's rigs with ancient fluids that seemed more like crude oil than refined lubricants.