I have an '07 XK. It has what appears to be a 195F thermostat that results in a coolant operating temperature of 200F-205F. I'd like to reduce the operating temperature to around 180F-190F.
The '07-'09s have "manifold injection", whereas the 2010+ have direct injection. I have noted at least one mfg (Hyundai) reduced themostat settings when it went to direct injection (same motor). My sense/guess is that mfgs use the higher temp thermostats on manifold injection for a very minute gain in warm-up emissions; and that motors run better in the 180F-190F range.
As an aside, 180F is not so low as to cause a motor to revert to open loop. My research source is A. Graham Bell, a UK tuner/writer now living in Aus.
Jaguar does not offer a cooler thermostat for the '07-09, and earlier XK8s use a completely different thermostat design.
My question for any owner of a 2010+ XK/XKR is what is your normal operating temperature as measured by any OBDII gauge, like a ScanGauge? If so, then perhaps your thermostat might interchange with my '07s. Thanks.