My 260Z has the 26 HP Liquid Cooled Kawi. Within the first week of owning it I noticed that I had to add antifreeze a couple of times to keep it in the safe range. I told the dealer this and I took it there and they tore the engine down and did a pressure check and whatever else. They told me that there was no leak and no problems and sent me on my way with a $400 bill which I fought tooth and nail and didn't end up having to pay. They said that this issue is normal from pressure in the coolant lines. I asked them why they didn't tell me this before tearing it down and they had no answer. Today, I changed the oil for the first time since they worked on it and I noticed a froth film in the dipstick tube and on the bottom of the dipstick. The oil looked normal when I drained it though. The pictures that I am posting are after I changed the oil and let it run for about 20 minutes. Do you think that this is just from a little bit of antifreeze that they got in there when they tore it down or do you think I have an issue? Here are the pics, thanks for the help.