I cannot imagine how you got 4k out of a tyre with only 1.7mm tread depth when the legal minimum is 1.6mm. that's 0.1mm in 4k? Sorry don't believe it, especially on a front wheel drive diesel. And 1.6mm is the absolute legal minimum, by which time grip will have almost disappeared, especially in the wet.
2007 C-Max 2.0l Zetec auto in Panther Black