How bad is this?

[cnl64590]

Hello BITOG experts, I changed my oil today (2003 Merc c320) with the usual stuff, Mobil-1 0w40 and a Mahle polyester filter. The shock and horror came when i opened the oil filler cap and found this:

This is my theory on it: The OCI for the car from the manufacturer is 10k miles and 6 months. I don't drive it nearly that much, so I change it seasonally (every six months). My usual OCI in mileage is around 3,000 miles. This last interval was 2,300miles and 6 months. Since the car sits for 4-7 days between drives, and the drives are usually short (not up to full operating temp), I imagine the oil had moisture in it (from temperature fluctuations) and did not have adequate time at operating temp to boil off the moisture. Thus, the oil had moisture in it and churned into the creamy dijon mustard aioli I found under the cap.

What should I do in the future? (shorter OCI or perhaps a long drive once per week?)
How harmful is this to the engine?
Is the oil (Mobil-1 0w40) any way at fault? Should I switch to something else like castrol or pentosin 5w-40?

Thanks guys for your input!

 

[Quattro Pete]

Yup, moisture condensation due to short tripping. Take it for a longer drive now and then, and you can even extend your OCI to once a year then.

The oil is not at fault.

 

[SatinSilver]

Did you clean it off or just re-install the cap? I'd try to give it a good highway run every 2-3 weeks. Probably 50 miles round trip.

 

[cnl64590]

I cleaned it all off as much as possible with shop towels. No way was i letting that banana custard hang out in my engine lol.

 

[Rand]

normal winter short tripping mayo.

Try to get it up to full temp at least once every 10day-2weeks.

and by that I mean drive it for at least 30miles.

 

[turtlevette]

Suddenly the messed up engine in my trans am doesn't look so bad.

Think about how much of that is on the inside of the valve cover.

 

[dparm]

That's way beyond normal "short trip build up". My cars see even more severe usage and I have never ever seen something like that.

I would tell you to do another oil change after 1000 miles to help flush the remains out. Do a lot of highway runs in there if you can -- 30+ minutes of sustained running at normal temp.

[censored], find some empty roads and do a bunch of WOT pulls to burn it up.

 

[spasm3]

As others said, needs some heat, longer trips, and make sure the engine is getting up to temp.( I.E. the thermostat is working properly).

 

[cnl64590]

I think I just have the perfect storm: Infrequent trips, Washington wet, cold weather, and I have an obscenely stupid driving style. I accelerate as smoothly as possible to make the trans shift up at or below 2,000 rpm.

My fault entirely; looks like I need to stick some lead in my shoes!

 

[turtlevette]

How's the antifreeze level?

 

[cnl64590]

Thankfully, exactly where it should be. I thought of that too when I saw the oil cap.

 

[Chris142]

Taste it. If it's bitter its coolant

 

[Trav]

Its very common given the conditions, its probably only in the cap area not down on the valve train as its the highest point.
Check the breather hose also, they can filled with the stuff.

 

[cnl64590]

I noticed there was a definitive point on the fill spout where it was regular liquid oil and not yellow cream. Good point, I hadn't thought of the breather hose.

 

[barryh]

You'll probably think this tedious beyond belief but if you can't fit in enough longer trips to get the oil properly hot just remove that filler cap after every short trip and let the engine breath until it cools down. There will be enough heat in the oil to drive off some of the moisture. No way will it shift a big build up like that but it will prevent it building up in the first place. I realise this only going to be realistic if the car is parked up in a garage.

I don't need to do this on my C180K because that gets minimum 10 mile trips but I used to do it on my old 190e and still do it on my motorcycle during the winter after a 4 mile commute. It's tedious but it works.

 

[oemjunk]

I don't no man. In all my years; I have never seen that before but once. It was in a an old t-bird I had blown head gasket. But you say no coolant loss. So that's good. Hope it's just moisture.

 

[marc1]

To answer your question how bad is this? It is not bad at all. It is from your short trips / limited warm up etc. It is not harmful.

A shorter OCI will certainly not stop this from forming nor will changing your oil brand. New oil will not get up into your filler cap (and other cool running areas you can't see) and wash or dissolve this away. Another brand will not wash / dissolve it away either.

A once per week trip on the highway for 15 minutes isn't going to make it go away either.

The only thing to observe and to be cognizant about this buildup is that you are in severe service category on your oil so use that OCI if offered in your manual.

 

[cnl64590]

Brilliant! That is a great idea. Thank you!

 

[Brybo86]

I kinda wish you had left it and took a 30 mins highway drive just to see if it changed at all

 

[69GTX]

If you're driving around in overdrive at 35-45 mph on those short trips you might select one gear down. That will speed up your warm up cycle (2000-2400 rpm) by placing more load on the engine. You could also block part of the radiator air (equivalent of a smaller radiator) to keep temps higher. If your car is reaching the normal coolant operating point in 1-2 miles it's probably not a faulty thermostat.