The temperature gauge on my recently purchased 240 rises to just above half way on the dial and then stays there with relatively little variation. I'm used to a third of the way up the dial being normal on most other cars. The previous owner told me that he had installed a non-OEM thermostat some time ago, and from the behavior of the gauge I assume that it opens at a higher temperature than OEM thermostats. So I called the Volvo dealer to order a new one, and they sell 88 and 92 degree C thermostats. He told me that it's a matter of personal choice, but most people seem to buy the 92C thermostat. I don't understand why a choice is offered -- surely the engine and its components are designed to run best at a single specific temperature? Any enlightenment on this would be much appreciated!