Yellow Jello-like goop in oil fill neck

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JAG

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FYI: We have a 2009 Subaru STI with 6000 miles. First oil change was done at 2600 miles with synthetic oil. I just did the 2nd change at 6000 miles. While changing the oil I noticed the oil fill neck had some yellow jello-like goop (mix of oil, water, and fuel) in it. It's not been that cold here and most trips are 20 miles. This tendency to form that goop is going to have to be watched closely especially during real winter temperatures. If you own a late-model Subaru with an engine related to what's in the STI, have you observed this as well?
 
The oil filler neck is close to the same on my 2007 Outback. Since it sticks out in the air a long way (and away from any heat from the head) it's going to get that gunk in areas with high humidity and short trips.

Interesting since my wife drives a lot of short trips but does work 2-3 times a week 30 miles round trip and nothing like that here. I just changed the oil yesterday and 7k miles on the oil change.

Since you have the turbo I guess it may warm the oil a little more than our NA motor and once it gets up in the filler, you get the goop?

Also, I don't know if your dipstick is like mine, but its REAL hard to get a accurate reading and EASY to over fill. If it was over it could cause more oil to go up the filler. My first oil change with the car, I over filled it by about 1/4 of a quart and it all came out the dipstick (blew the dipstick out) and over the engine/hood.

Take care, Bill
 
Bill, it's my understanding that the non-turbo engines are very different in terms of their effects on oil and the amount of fuel dilution they cause.

Yes you are right about the neck being a prime place for condensing blow-by to form.

The dipstick in this engine is easy to access and check the oil fill level accurately. That's wild that your overfilling caused the dipstick to pop out!
 
I take it that you don't have a UOA on this, JAG. It would reason that you shouldn't see the emulsification in that type of service. Not being intimately acquainted with your engine setup, I don't know if there are other co-accessible (water cooling on the turbo, perhaps, etc.) points to moisture intrusion.

It would have my spider sense tingling on HG issues. Really, it would be more along the lines of a fear factor, but I think you already know that.
 
The yellow goo is from water/condensation/moisture in the oil. it "usually" comes from not allowing the engine oil to come up to operating temperature to boil off the condensation, which usually takes 30 minutes.
 
I think he's got that part. I think he's looking for other Soobie owners to find out if it's a characteristic symptom of the engine and not another issue. 20 mile events should make this condition a non-issue unless it's something like the Chrysler (2.7?) that had the lame PCV setup that produced this routinely regardless of operational style.
 
Originally Posted By: Gary Allan
I take it that you don't have a UOA on this, JAG. It would reason that you shouldn't see the emulsification in that type of service. Not being intimately acquainted with your engine setup, I don't know if there are other co-accessible (water cooling on the turbo, perhaps, etc.) points to moisture intrusion.

It would have my spider sense tingling on HG issues. Really, it would be more along the lines of a fear factor, but I think you already know that.


That's what I think too. I would want to do a UOA to see if there's any anti-freeze markers in the oil and it's not just condensation. Subarus are known to have HG issues. Supposedly the issues were fixed long ago, but some say they weren't completely fixed.
 
Same thing happens on the Dodge 4.7V8 with it's composite filler neck sitting a mile high above the valve covers. It also happens a tad on the TOyota's 4.7 but only on the bottom of the filler neck cap. THe filler neckon the Yota is machined Aluminum so it get's hotter then those composites ones so you never see it on the tube just onthe cap. If Yota had made that filler neck out of plastic it would have the same problem.
 
Update to this old thread. The STI now has 10,400 miles on it and I just did an oil change. It has used Valvoline Synpower 5W-40 MST since I started this thread with ~3750 mi. OCI.

What was previously goop has now become as hard as lacquer! I first wiped it with rubbing alcohol which did not get it off. Then I sprayed brake cleaner on it and let it sit for about 10 seconds and wiped it again. Even that couldn't get it off. I then scraped it with a flat screwdriver which caused part of it to chip off. I left it at that. I'm going to wrap a sock around the oil fill cap and neck to keep it warmer in the hope that this will lessen the tendency of vapors to condense there. I'm just amazed that this the lacquer formed in so few miles using good (maybe not great) synthetic oils with ~3750 mi. OCIs.

In the oil fill today I mixed in 1 qt. M1 15W-50 EP and 1/2 qt. Redline 5W-30 with the Valvoline Synpower 5W-40. The purpose of the M1 was to use it up and the purpose of the Redline was to get some esters in the oil in the hopes that it may lessen the tendency of lacquers to form.
 
That makes me feel unfortunate and it doesn't surprise me considering the big differences in UOAs for the 2.5L turbo engines and the 2.0L turbo engines.
 
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