I have read a few GRs from some vintage organizations, et al, and when they refer to competition, this is mentioned, and the requirement seems confusing. We use coolant that has anti-freeze/coolant all year long, and it provides good cooling on warm days, but if you go to one of these places, what would you do? I think water by itself would be a disadvantage in terms of cooling efficiency.

Should you just drain the antifreeze and add water before you leave home (unless you have a team trailer and a supply of water?) If you just drain the cooling system, there will still be small amounts of antifreeze in the mix; would they allow that? It's probably a lot better than several gallons of slimy, full-strength coolant on the pavement.

If you drain the coolant at home, would that handle the cooling requirements of driving to the event (which may be a hundred or more miles!)

Plain water will be fine. Most racing sanctions will allow WATER WETTER which will help with cooling efficiency a bit. Check with your racing organization.

Red Line Synthetic Oil - WaterWetter® Coolant Additives

Plain water will be fine.

I understand what you mean, but I'm sure the coolant companies would say you are inviting engine failure!

What do they use for NazCar?

Water is almost 2X more effective at heat transfer than antifreeze (ethylene glycol). The main point of using antifreeze is for dropping the freezing point, increasing boiling point, as well as lubricating the water pump and protecting the insides of the engine from corrosion. "Water Wetter" does the same thing.

Can you just use Water Wetter in place of Standard antifreeze? If you're not driving in the winter, then you don't really need anti-"freeze."

The only time my street Z or the race car have anti-freeze in them is in the winter as protection against the possible loss of heat in my garage.

Both get flushed out in the Spring and I add DI water and non-green colored water-wetter (red lets the track inspectors know you don't have coolant in the radiator). A coolant spill on a race track is a very bad thing

I ran 33 miles on the track today with ambient temps in the low 80s and my water temp gauge never got to 180.

So you only use the Water Wetter?

How are you flushing the cooling system to get all the antifreeze out? May I assume you re-use the antifreeze if it's still good?

Straight water with a bottle of water wetter is fine for cars that will not see any freezing weather. That's what I ran in my race car. On my street car I ran about 10% anti-freeze to water. To flush, disconnect the upper radiator hose, cap the upper inlet in the radiator, and run and hose into the radiator cap. Start the engine, turn on the hose, and watch the mess.

I drain my 50/50 mixture into a few gallon jugs and flush the system with water. I then fill it with distilled water and add Water Wetter. At the end of the racing season, I flush it again and pour the old 50/50 mix back in for the winter. I used to drain it and leave it dry for the winter, but it took forever to flush the rust out in the spring.

You're not just letting the stuff fall to the ground when you flush it? It sounds like you end up with gallons of contaminated water to get rid of.