AO Silver Member
Join Date: Mar 2003
Its going to vary a lot not only the time of year but with the type of driving. The times when the stat should be closed or partly closed will affect it most. So lot of short journeys (slow or minimal warm up) and higher speeds (the radiator being over-cooled) will make it worse. Perhaps up to a 15% increase in consumption.Or as little as 5% if its being used for medium length journeys at less than 40mph.
Either ways its probably worth doing as a buyer could easily spot the temperature gauge is slow to move on a test drive and then feel the top hose. Poorly maintained car could mean a lost sale.
edit: If you do change it and find a noticeable improvement you could also convince yourself its worth keeping it!
'A business absolutely devoted to service will have only one worry about profits. They will be embarrassingly large.' - Henry Ford.