2012 Ford Focus, 155K miles, it is leaking a decent amount of coolant when my partner drives it to work but doesn’t even leak a drop if I drive it to work. The mileage is the same but I don’t sit in traffic. Could the extra heat from sitting in traffic be opening up a pinhole sized leak in the coolant line?
Edit: Thanks to a tip from the comments when the heat is turned on it leaks. I should be able to bypass that line pretty easy.
If its head gasket I would expect the loss to be consistent. If you open the rocker cover cap / oil filling point and it looks like there is Mayo in there, then it could be a sign the head gasket is failing.