2003 Outback, 113,000 miles
New water pump and thermostat (replaced twice)
Below 40 degrees, starts to overheat. Is controlled by
1. making sure the heat is turned on high -- if temperature gauge doesn't come down, then
2. put blower on full and then the temperature comes down within 60 seconds.
Occasionally, even with that, the gauge may fluctuate and then I bring the speed down to 60 and it gets regulated.
It does not happen if it's above 40 degrees and the Subaru dealer cannot replicate the problem.