Been there @ 75k. Was topping up approx 250 miles 1 pint, then it went to 100 miles....

Pipe that runs for a 1 way flow valve for the EGR cooling jacket (for me), runs between the V-6 inlets, one bank has to be removed for access... part cost £6 (plastic in-line), labour £500. inc, pressure testing. It was a bummer as I had to pay for anti freeze for the second time in 6 months (first time water pump @70k).