Oak tree leaves
This looks like an environmental issue, not insects or disease. We can't say from the photos was is causing the discoloration. It may have been caused by some substance or high temperatures nearby.
Monitor the tree. If he sees new or different symtoms, send us more photos.
Here are additional pictures which I hope will help determine this oak tree issue.
Thank you for your further input.
Here are 3 more pictures which I hope will help determine this tree's issue.
(I sent this once already, but I'm not sure it went through since I did not get an automated response.)
Again, we are not seeing anything to be concerned about. As previously stated this looks environmental and not insect or disease related. If you should have any other concerns about the tree contact a certified arborist for an onsite evaluation of the tree.
The following website can help find an arborist.