With cool weather approaching, fall is the traditional season in which to service your Volvo's cooling system. Most people give the system a good flush with a cleaner and renew the antifreeze at this time.

Here's a very simple tip that can greatly extend the life of your radiator, water pump and soft plugs: use distilled water in your cooling system. Buy a gallon or two at the supermarket -- it's one of the cheapest nice things you can do for your Volvo (actually, the tap water where we live is undrinkable -- we refill our water jugs for 25 cents a gallon at the vending machine outside the store). Even soft tap water contains ions which make the water a good electrolyte, and this makes corrosion possible.

Antifreeze should be mixed according to the manufacturer's directions, usually in a 50/50 proportion with water. Antifreeze has three benefits: it freezes at a much lower temperature than water (that's the obvious one), it vaporizes at a somewhat higher temperature than water, so your engine can get hotter without "boiling over," and it contains corrosion-fighting compounds to offset the fact that ethylene glycol, the main component in antifreeze, is corrosive in its own right.

Antifreeze also has two negative qualities. First, it is extremely toxic if ingested -- always capture coolant containing antifreeze when draining and recycle it! Many states have laws requiring stores that sell antifreeze to accept old coolant in return.

The second negative (we've had some argument about this, but we'll stick with it): antifreeze transfers heat less effectively than pure water and reduces the overall efficiency of the cooling system.

If you live (as we do) where it never freezes outside, and you have an older Volvo designed to run at relatively low temperatures, you might consider not using antifreeze at all. In this case, fill your Volvo with the distilled water and throw in a can of corrosion inhibitor / water pump lubricant instead of antifreeze.

A final tip: when you service your cooling system, spend a few dollars more and an extra five minutes and install a new thermostat. The thermostat is very important in maintaining your engine's optimum operating temperature. This is important in any car, and is a critical factor in the proper operation of fuel injection.