Oil in Coolant after Cooler rebuild

[Silvercrew]

Hey all, I just had my oil cooler o-rings replaced and new gaskets put in. Had this done last week and this weekend I decided to look in the degas bottle and noticed a small amount of oil floating on top of the coolant. It is just enough to show up on top of the coolant in the first chamber of the degas bottle. Could there have been a little bit of cross-contamination of oil getting into the coolant passages when the oil cooler was worked on? I will continue to keep an eye on it but in the past 200 mile the coolant level hasn't increased and the oil level has not dropped and there does not appear to any coolant in the oil. I am intending on flushing w/ some ELC very shortly but now seeing the oil in there has made me slightly paranoid . Also, how do you tell the difference between oil in the coolant and diesel in the coolant. Mine appears to be a couple of dark "globs" floating on top with the oil-slick type appearance on the surface of the coolant. Thanks!

[mgassel]

Your coolant will have a sell of diesel if diesel is in it. Your degas bottle will be kinda brownish on the sides.

[mgassel]

I had fuel in my coolant and just got my truck back from the mechanic because it needed injector cups.