I use one gallon of coolant and fill the rest with distilled water which should be somewhere around a 60 water to 40 coolant mix I think.

The issue with less than 50% water is corrosion protection. It says so right on the back of the Toyota Red Long Life Coolant bottle. This stuff is supposed to be good for a 50K change interval. The boil and freeze temps are not going to be an issue unless you are in a seriously cold climate. Water is actually a more efficient coolant without the ethylene glycol. That's why you should never go over 70% anti-freeze.

So I would keep it to 50/50 if you insist on running a 50K change interval. But I bet you are fine up to 60% water if you live in a non-extreme cold climate and keep your change interval closer to 30K.

Take into consideration that there is also some fluid left in the block and if you don't remove that plug that's probably .25 quart anyway. The 9.3 qt capacity is bone dry specs.

Also I was thinking about catching my old Toyota Red in a clean bucket and after adding the new gallon of red and gallon of distilled water if I need to add some...use the old red to top off.

Oh hey 5 years ago, you called?

I swear the Toyota red coolant container said 100k miles.

Which is basically good for next water pump change.

Yeah TheDurk is right, water actually cools better than coolant does and having a tad bit more water to coolant wont hurt a thing but slightly affect the freeze point which would still have to be crazy super cold before it would even think about freezing up.

So why does the maintenance schedule for my 2000 show to replace the coolant every 30k miles?

Can you top off original Toyota red with zerex Asian red? Because that's what I did recently.

A gallon of red straight coolant from my dealer was $20 bucks. That's $20 bucks for 2 gallons of toyota red coolant basically after you distill it.

I just did the coolant replacement as part of the timing belt and water pump job. I purchased several gallons of distilled water. With one half full jug of water, I added the other half as TOYOTA RED. This was an easy way to "eyeball" the 50/50 mix.

I have always run 50/50 here in the Hades Hot state of Alabama. Taking the water pump out and thermostat, they were clean as a whistle. No corrosion or white powedery buildup anywhere.

I know it might be my OCD, but I ALWAYS use distilled water and I think this has a lot to do with the cleanliness of the cooling system. City water/tap water/well water can all have significant amounts of chemicals and mineral deposits. (These are not good for any cooling system). The distilled water is just about as "pure" as it gets. I would recommend using distilled water and Toyota red. You can't go wrong doing that! (I'm saying that with my rig being 18 years old and on the brink of 300K miles....she still purrs like a kitten and gets good gas mileage)

I was thinking this exact thing, glad I came across this thread. It's anti-pink-milkshake radiator replacement time. I've got rear heaters, so apparently my capacity is 9.3 quarts. Half of that is 4.6 quart. Buying a second $25 gallon of Toyota red for that 0.6 quart (if I were to drain the block, which I'm not planning on), is an annoying thought. My current red looks very clean as it is, and my area virtually never gets below -10F. I very well might use extra distilled water or a little of the old stuff to get that last ~1 quart.

I realize this is an old discussion, but one point that wasn't touched on and it should be noted, yes water is better for cooling, but anti-freeze/water 50/50 raises the boiling point to about 220*F, our motors should run between 190-200*F for optimal fuel efficiency at operating temp, this becomes even more important for those of us travelling in high altitude. It also should be noted that pressure inside the cooling system also raises the boiling temp, but a 50/50 mix is ideal in almost all situations/conditions regardless of outside temp and elevation.