's wrong, mind, for most use, IME.

for mostly-on-road, I'd go for 36 all round.  28 front is definitely on the
soft side with a diesel, and unless you habitually carry a fair amount of
weight, 38 may be a tad on the high side at the rear.  if you run light most
of the time, I'd expect slightly too much tyre wear in the centre.

I run mine on 235/70s at 36 all round, and also ran 205s on a 300 TDi at
that.

it makes the ride a tad harsher on small sharp bumps, admittedly, but the
tyre wear patterns are more sensible.