Thermostat warm up time

Any one know the suggested warm up time on the 1.6turbo iesel.

Changed the thermostat on weekend and once warm it sits st 82 degrees and he mpg is good

But my wife dives 10 miles urban to work and her mpg is around 41

Any ideas how to speed up warm up? Is there only h thermostat or does the egr have one as well?