I meant how long does it take to attain normal (needle to the middle) working temperature?
If I start the car, and leave the engine on idle state then it takes 7~8 minutes to reach the central mark.
Does it climb quickly to the middle?
If I start driving just after starting the engine, then it reaches the centre mark in 4~5 minutes.
If you pick up speed on the highway does the temp fall or stays there? Do you have the thermostat valve installed?
No, it remains in the centre position regardless of the speed factor, however with the AC switched on at highways, I have noticed that the temperature needle drops slightly from the middle mark.
Yes T-stat valve is installed and fan is on auto.
Also, how is the condition of radiator water? Does it seem to be dirty?
Nopes, its clean but has a orange colour due to the coolant.
When engine is running are there any bubbles coming from the water?
If I open the radiator cap, 5 mins after switching off the engine then I can see some small bubbles of water at the top.
Was the radiator cap (inner side) oily/milky or have any grime or deposits etc?
Nopes, no such issues.
Its inner side including the rubber seal were clean.