This is what came out of reservoir.

 

Oil and coolant don't mix very well. When I had oil in coolant and vice versa it was immediatley obvious. By those pics it doesn't look like it, but I dunno wtf that is.

 

can't tell from the pic - rust maybe? how old / how many miles?

 

doesnt look like it... oil and coolant mixing becomes a vanilla color. youll notice it when you have them 2 mixing.

 

flush the coolant. And check your radiator for corrosion.

 

not sure what that top pic is of but the second pic does not have oil in the coolant. i just replaced my radiator and coolant and thats exactly what came out of my reservoir. maybe it's time for a flush or possible a new radiator.

 

I just got a valve job on my 99 integra non vtec. I started to see this stuff in the filler neck and I thought it was oil. The amount of this stuff was consistent every time I checked.

I did a leakdown and everythink was great. My oil is clean and the coolant level remains the same. I just got done removing the thermostat and did a complete flush.

Hopefully it doesn't come back! Thanks for the help.