Coolant recovery tank
your coolant tank should be on the pass. side inner fender
Engine coolant.
The Owner Guide shows Ford Extended Life Engine Coolant ( orange )
in the coolant resivor
When the engine is cool
In a 1999 Chevrolet Cavalier, you can add coolant to the overflow reservoir, which is typically located near the front of the engine bay. The reservoir is usually marked with a "coolant" label and has a cap that can be unscrewed. Make sure to check the coolant level indicator on the side of the reservoir and add the appropriate mixture of coolant and water if necessary. Always ensure the engine is cool before opening the cap to avoid injury.
If no cap on tank must use reservoir.
No, you should not put diesel coolant in a gas engine. Diesel coolant is formulated differently and may contain additives that are not compatible with gas engine cooling systems. Using the wrong coolant can lead to corrosion, overheating, and potential engine damage. Always use the coolant specified by the manufacturer for your gas engine.
In the coolant reservoir in front of the engine.
The TTR125 uses an air cooled engine, there are no radiators to put coolant in.
They come from the factory with a 50 / 50 mix of antifreeze and distilled water in the engine cooling system
I would only put water in an emergency situation where I don't have coolant available. The coolant helps the engine to not overheat and to not freezing, while that could happen if you just use water. If you don't have your vehicle's manual to know the specification of the coolant, you can use the generally available Prestone and add water according to the table on the coolant's recipient. (or you can buy the pre-mixed formula)