Bassrock

Right, My external temp sensor appears to be reading 10-15 deg higher that it should, certainly was not 29 deg C in bonnie scotland on 19 March 06. How do you test sensor eg how many volts per degree or how easy is it to change, looks a sod and can't figure out how to do it. Any advice out there. PS my fuel consumption appears to be increasing as well eg currently at 37.2 mpg (average average), normal was somehere around 39.2, but no engine management warning yet. Could the two be linked ??