There's this white slimey stuff all on the walls of my oil filler neck. I ran my finger through it and it looks exactly like what i'd cough up if I was sick. Its like snot. Milkey white. Engine doesnt seem to be having any problems running and oil consumption is normal.

On a side note, I have 850x4 and a strange idle that I cant really solve. My rpms bounce between 1k and 1.3k. Runs way to rich at idle, and I cant stop it with the AIC. Anyways, it revs up to 1.3, then drops for a second, then revs up, then drops. Well, right after it drops a little bit of smoke will come out the side of the oil filler neck (where I have the vent uncapped). The smoke is only there for a split second, then disapears. My coolant level is perfect and I havent touched it in 3k miles.

So, WTF.

 

you need to vent your crankcase (stock emissions crap).. or what you can do is drill a hole on top of your oil cap and fit in an L-fitting for it to vent

 

This is totally normal. ALL RX-7's get this to some degree. It's caused by condensation mixing with oil vapors.

Even brand-new RX-8's get the milky oil cap stuff.

Dale

 

It's just condensation in the oil; no worries. The filler and cap is the highest point so that's where it collects.

Those of us who often drive our cars hard never see it though

 

Don't worry about it, it's normal. Don't try to do anything about it.

 

do something if something was done to make it worse than normal, like no t-stat and fans always on during cool/cold weather, etc.

condensate formation is based on water included in gases bypassing the combustion seals on the rotors. short trips in cold/cool weather, where oil/engine temps stay low, increase it's white-ish formations. use oem 180F t-stat, and at least a 195F fan set point.

the PCV valve will also help reduce water vapor bulid up in the case, by purging with ambient air from the air filter, during idle and vacuum driving conditions.

 

Oh. It already vents to atmosphere

 

Really that’s interesting, I haven't heard that before. I typically drive my FD hard nearly every weekend, and I still see that mixture on the oil cap. Now granted it sits during the week, and its not driven nearly as hard as an open track day. But I'll admit I tend to drive my car pretty hard, I am WOT and redlining multiple gears usually at least a few times every time I drive the car during the weekends. Given that, I assume that sitting during the week causes this build-up despite being driven hard during the weekends.

Although as you mentioned, I don't recall seeing any build-up during the summer months. It was only when the temperatures started to decline up here in Michigan. I recently changed the oil last week to my winter weight, and I noticed the mixture. I also have coolant temps around 185-190 and dual oil coolers.

No biggie as I know it’s completely normal, just thought I would throw some more information into the thread.

 

did it get its flu shots this year?

 

Some oils seem more susceptible to this than others, also..

I only ever had this happen with Castrol Oils..

I use Shell now, and clean as a whistle...

 

It's just as KevinK2 explained. The moisture in the oil condenses into vapor and then collects inside the cap where it looks like a milky film. I drive my car daily and absolutely never see it because the oil gets hot and evaporates the moisture out constantly.

 

Hrm, funny thing is its Castrol Syntec

 

I'm not surprised...

It would be interesting to know how many other people use Castrol and suffer this, vs Other Oils...

The first time I ever saw this was years ago, on a small-block Chrysler V-8 which had been run on Castrol all it's life.. the sump was so full of sludge that it only took about two pints of oil Very extreme case though... as others have said a good long run will clear most of it up...

 

If I had $1 each time a newb asked this question, I would be rich.
This happens to many cars besides RX-7s.

I suggest that it and the turbo gurgling sound be placed in the FAQ folder.

 

I use regular Castrol dino oil and have never had this problem.

 

i also use Castrol Syntec and i have the same thing in my oil filler neck

 

Hey, I never said my theory was PERFECT