Coolant level/top up

[Distress]

Reviewing owners manual for 06 ACV40R it states that coolant level should be checked when cold and should be between F and L marking on the bottle. Inspecting coolant in this setup the coolant level is below L mark, atleast a couple of inches. However when engine is at normal operating temperature, coolant is at exact middle between marking. I have not experienced any cooling/heat issues with the car however wondering if coolant should be topped up. Coolant still appears pink/red so

not noticeable rust presence.

The service schedule does not mention any coolant replacement until 150,000/10 years so I am certain it has never been changed. There is no leaks of any kind. Question is - should I top up coolant at this stage or just wait out the service time? My guess I will be mixing original Toyota coolant with aftermarket of same type. Is there any adverse effects in this case as obviously mixing chemicals never good idea. Top up will likely be with an aftermarket coolant of same type (super long life of red color) - http://www.autobarn.com.au/nulon-red-top-up-long-life-coolant-rlltu1

[Tard]

Personally, I aim to have the overflow bottle to be at about 3/4 full when the engine is at operating temperature. This should allow sufficient room for expansion should it need (in a worst case scenario it will just overflow out of the tank) then gives more than enough coolant available for the cooling system to pull in when the engine cools down. Having it mid-way at operating temperature is fine however provided that when the engine is cold, there is still fluid above the level of the tube that extends into the overflow tank.

[Distress]

Thank you for input. Definately will aim to raise level as a precaution. Having researched further on the coolant, Nulon appears to comply with toyota specs so should be just a straight top up.

[Hiro]

As far as topping-up the radiator or coolant overflow bottle is concerned, if you're not 100% certain of what coolant is in the engine just use distilled water (or even tap water if you're not completely anal or your local source isn't liquid calcium). The quantity you are adding is relatively small in comparison to the volume of the whole system so the dilution factor will be minimal (just don't do it over the long term as you'll eventually reduce the concentration too low).