I was impressed with the dealer not charging me. He said he had several hours into it and I was expecting to have to argue about the bill, since they convinced me to bring it in. But no arguing required.
I appreciate your input and it's obvious that you know this subject well. Even better than the dealer, since his tech was not aware of the engine changing at 27*C. He eventually found that it was due to an increased fuel flow at that temp. Well, that is what he told me.
I find it difficult to determine if someone offering expert advice (on the internet) is in fact an expert on the subject. I've had lots of so called expert advice from people proclaiming to be knowledgeable on a subject matter only to discover their recommendation to be flawed or just wrong. Not so in your case and thanks again. Even my dealer learned something from you.