I took my car to the dealership for an oil change and inspection, which includes the fluids being checked and topped off. After the service, I took a look at the fluids in the car.
There is a tank marked "coolant" with
L marks on it, and the the level of fluid in this tank was (significantly) below the
L mark - it looks like there are about two cups total at the very bottom. I understand that this is the expansion/reserve tank that is used when the radiator requires it, and captures extra coolant when it expands.
I asked the service manager about this and he said that it was normal (even for the level to be below
L) and that I should "check my owner's manual" to verify. I was somewhat dubious of this, and my owner's manual says the following:
The coolant level should be filled between F and L marks on the side of the coolant reservoir when the engine is cool.
If the coolant level is low, add enough distilled (deionized) water. Bring the level to F, but do not overfill. If frequent additions are required, see an authorized dealer for a cooling system inspection.
When I checked the coolant level, the engine was still warm and not completely cold. Could this have caused the coolant reserve level to be lower than usual? Is there another reason that I could have observed this, or is the service manager pulling my leg and the mechanics neglected to check the fluids?
Should I add fluid to this tank myself? Why distilled water rather than an antifreeze/water mix?