Sludge underneith oil cap

[firebirdguy]

when i bought my 08 v6 4runner it had a very heavy yellow gunk on the cap as well... a 4 hour drive home at 80mph did not get rid of or reduce the gunk at all, so the comment above that your 300 mile trip didnt get rid of it is correct, once its there you have to manually clean the cap. from that point monitor what its doing, daily short(er) trips in cold weather can cause it to come back. & synthetic oil doesnt contribute to or decrease this, its simply from condensation not being fully burnt off in the oil & the long filler neck cooling much faster than the rest of the engine allows it to collect on the cap. once i cleaned my cap it has never came back but, i try to avoid short trips, especially in the winter & i live in iowa where winter temps can be & usually are well below freezing if not into the single digits & below zero... like the next week of single digit highs & -10 to -20f lows. i also do not use a catch can & after over 1 year & 5000+ miles the cap is clean as new.

also a few other points to mention, heet doesnt really "prevent" water/moisture from forming in the tank, its intended to remove moisture thats already in the tank. as you mentioned, condensation happens due to temperature changes & high humidity in the air etc, it will form regardless of what additive is in the tank. heet is just alcohol, ethanol fuel will do the same to remove water in the gas... but regardless its not water in the fuel that is causing the yellow gunk under the oil cap, its moisture in the oil & condensation forming under the cap.

windage trays do not remove vapors, they are intended to control windage, or air/oil turbulance & aeration to keep the oil itself & droplets from hitting the fast spinning crank counter weights & rods therefore reducing power.

im sure if you clean the gunk off the cap & try to schedule your trips so they are at least 20-30 minutes of driving after reaching operating temps it should not come back or will be greatly reduced. that worked on my 4runner with gunk almost as bad as yours, the prev owner was a soccer mom & probably drove 3 miles to the grocery store or other very short trips causing the issue.

 

[V8Man]

Guys that's water and it's combining with the additives in the oil that are there to remove or hold the water until it’s evaporated by the warm engine.
This happens when you take short trips where the engine doesn’t get to full temperature for a extended time. Check the operating temperatures or the operation of the thermostat.
A faulty PCV will cause this too. The condensation leaves the engine oil and is rerouted to the intake to be passed into the exhaust.
Hopefully your engine isn’t experiencing a head gasket failure which is another way water shows in the oil.

 

[Lucas606]

A little bit of build-up is normal and Is nothing to worry about. I had a little on my last oil change but it went away after that. You only have to worry if there's a good amount under the cap because then you'll be looking at getting engine work done.

 

[Drcoffee]

The oil sludge is the result of moisture condensing in the oil fill tube. Think of it as a cooling tower. All metal 8” tube being cooled by the radiator fan continuously in <40*F weather. Like a distillery.

Try insulating the fill tube so it remains hot. Wrap it with silicone tape. Id bet the sludge is reduced.

High school chemistry

 

[U.G.N.]

Today I found the same creamy "coffee with milk" color substance under the oil filler cap. I own this 4Runner for over 7 years and it never happened before (I did drive it less over the last year and half about 4,000 km every 6 months and rotate it with Lexus LX 470 on a monthly basis).

Also several days ago a cloud of blue smoke came out from the tailpipe as soon as the engine started after a cold and humid night and then it changed quickly to white smoke. And she started rough this time. I have not noticed this blue smoke in the past and changed engine oil for fully synthetic Mobil 1 EP 5W-30 about 3 months ago. I drove it less than 1000 miles since the oil change.

Should I change this Mobil 1 EP oil or leave it until the next scheduled oil change?