170K miles. temp guage does not register (needle sits below 'zero'
line) until engine is warmed up *and*
accelerator is let off *and*
is not slowing down.
for example, letting the accelerator off on a slight downhill on the
highway causes the needle to swing up to normal op temperature over
the course of a few seconds. as the car slows, it tends to drop back
down to below the zero line.