I'm switching from old standard green coolant to the RED OAT coolant.
Most articles say its compatible but I found one article that said
it should have less than 25% contamination. It was also recommended that
I remove the drain plug in the block to get more of the old stuff out.
I thought about that, found a couple of reasonable candidates for drain plugs
but decided to leave well enough alone.
Instead I'm doing a number of flushes with distilled water. The math say
I should be below 6% old stuff when I get done. I able to drain about 4-3/4
gallons just using the petcock on the radiator. The math follows: feel free to check
my math. I did the calculations assuming I'm only getting 4 gal out, its easier
starting assumption: 50:50 mix, math folks know that as a 1:1 ratio,
that is 4 gallons of coolant, and 4 of water or 50% coolant.
The system holds approx 8 gallons.
Remove 4 gallons, that leaves 2 gallons of coolant and 2 gallons of water.
Add 4 gallons* of water, Now I have 25% coolant.
Step 2; get engine hot and let it cool off to mix it all up.
Remove 4 gallons, that leaves 1 gallon of coolant and 3 gallons of water,
add 4 gals of water*, Now I have 12.5% coolant. that is 1 gallon coolant, 7 gals of water.
Step 3; drive around.
remove 4 gallons, that leaves 1/2gal coolant, and 3-1/2 gals of water,
Add 4 gallons* of new OAT coolant, that leaves about 7% old coolant,
which is way below the worst case spec I could find. and since I
was really removing almost 5 gals each time, it should be good.
I'm sure there is a fancy equation to give the correct number, if you know
it I'd love to learn it. It must be some kind of series math thing.
*Adding the 4 gallons back is a two step process. Only 2 gallons fit in the
radiator and it blocks a 2 gallon size air bubble in the engine.
I had to run the engine for a bit, let it cool off and
then the air bubble moved to the radiator so I add the other 2 gallons.
Make sure to store the old coolant away from animals, neighborhood cats etc.
Its highly toxic. I found 4 old plastic milk jugs and reused the jug
the distilled water came in. Then I found an environmental friendly garage,
in my case it was a goodyear tire place, that took the old coolant for recycling.
I'll be giving them first rights to my new tires. One hand washes the other
and we should reward corporations that are doing right; its so hard to find
that in the current business world.