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I've had plain tap water in my car for about 15 months, and flushed it every 5 months or so. I was thinking about puting coolant in, but not sure if it's worth it.

Is it?

Coolant is Anti corrosive, anti boil, anti freeze and it cools quicker and stays cooler longer. Plus you wont have to be changing it every 5 months... depending on the coolant you may only have to change it every 24 months or so. your motor will last longer running coolant rather than water.

I would say it's worth it.

Dave

Yeah there must be a reason why they suggest you use it

Tap water will leave deposits throughout your cooling system; in the radiator, water hoses, engine, heater core etc. These deposits are usually a brownish sludge and what this does is inhibit heat transfer to and from the coolant. Its never ever a good idea to run tap water when there's an alternative available. Tap water is waaay too dirty for the job... if you've ever looked at a well used kettle you'll see the same thing.

Really the only alternative to proper coolant is deionised water. So really what you should be asking is whether to run:
a) deionised water
b) glycol based coolant
c) corrosion inhibitor
d) all of the above.

Correct answer is dependant on the stresses the motor is placed under.. if you live in a very cool climate you'll want glycol based coolant as this lowers the freezing point of the water. Glycol isn't that great though, it lowers the amount of heat that the coolant can absorb. Corrosion inhibitor is a fairly essential thing in an all alloy engine like a Subaru, but in particular its required in alloy headed steel motors.


So I think you can guess my answer... stop running tap water!! In my own Subaru engines I run deionised water and Redline WaterWetter, mind you thats a very effective non glycol coolant with very average corrosion inhibitor properties. Probably not the best choice for a daily runner or that old EA thats done about a squillion km's.

Coolant is better. Thats why every car manufacturer recommends you use it and all cars are shipped with it in their radiators.
Water is cheaper but I can't think of any other reason you'd want to put it in your engine. Sand is cheaper than oil, could put that in instead of oil too I suppose

Anyone who uses tap water in their radiator ( esp an old EA ) deserves to have their engine blow up.

I think that settles it then!

Last time supacheap had a 20% off sale I stocked up on coolant so I guess it's time to put it in, now that I'm not constantly disconnecting the cooling system all the time.

Coolant Ftw!!!!