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What Coolant Antifreeze to Use For Buick Grand National?

Here’s another answer in our “what type of liquids to use in Buick Regals” series.

As more and more Buick Grand Nationals, Regal Turbo T’s, T-types, Limiteds, GNX’s and all of the other varieties available of these GM Gbodies trade hands, the knowledge of what to do on them, and the products or processes that should be done to them, aren’t always passed down to the new owners.

And as the long-time care takers of these awesome vehicles will tell you, they aren’t really like working on any other car.
They require a totally different approach than other brands or models do.
Yes, some things are “almost” the same as others, but certain areas need a special touch to make them function properly.


Note that depending on what region of the Country you live in will determine what you should or shouldn’t use. If your area gets cold snowy winters, you need some kind of antifreeze protection! Warm weather year round (Florida, California, etc.) can get away with using only something like RMI and water.


Turbo Buick Regal owners say:


I use 50-50 Prestone and water in the winter with a bottle of RMI, and distilled water and RMI in the rest of the year.

Distilled water plus RMI-25.

The only product I have found that cleans, lubricates, inhibits and conditions the cooling system is the RMI-25 radiator additive.
(commercial and industrial field use for over 30 years has proven this)

RMI-25, with tap water or bottled water.

Pre-mixed Prestone AntiFreeze / Coolant with a bottle of RMI-25.

I use the water wetter and RMI together. I have found the water wetter to actually reduce temperatures greater than the RMI, but the RMI cleans the radiator better. Back to back testing was 10 degrees cooler with water wetter.

Prestone Extended life is what I use now, good for 5 years, I change it out every 4.
Daily driven every winter. I use the full strength stuff not the 50/50, with tap water.
Don’t buy the 50/50, full strengh is not much more money and you don’t pay for a half gallon of water.

I use whatever brand of anti freeze is on sale and never had a problem.

I use a 50/50 anti-freeze mix and about 4 oz of RMI-25 to help cool and keep system clean.




The owners manual says cars with A/C have a coolant capacity of 16 quarts.
Non A/C cars have a 15 quart capacity.



It’s a good idea to change and flush the radiator once a year.
(maybe twice for better reliability and performance, depending on what products you use)
Process: Drain, flush, clean, flush, refill.

The usual fill method:
Pour in 1 gallon of (full strength) anti-freeze, any additives, then fill the rest with water.

DO NOT mix different colors of anti-freeze.
There have been a number of problems with changing from one type of coolant to another.
IF you’re going to switch colors, BE SURE to completely flush the entire system.

The orange anti-freeze was designed for aluminum engines/parts in new cars.
However, it doesn’t last as long as the green coolant.
If you use it make sure you change it out once a year.





Water transfers heat from metal surfaces much better than antifreeze.

More heat is dissipated from the engine and transfers it to the radiator.

The radiator cools the mixture, runs thru the system, and the whole process starts again.



Distilled water (by itself)
is corrosive to certain engine parts.

So be sure to use an additive for water pump lubrication and corrosion inhibitor.

Can shorten the life of the water pump.


ANTI-FREEZE (ethylene-glycol):

Helps cool the motor along with the lubricating ability for your water pump.

A 50/50 mix is good to minus 34 degrees F.

Drawback (especially race cars):
It only takes a small amount to contaminate the oil if a head gasket blows.
This small amount is enough to ruin bearings.



The general consensus is that it indeed lowers temperatures 10-25 degrees.

It mixes well with most any antifreeze product.

RMI and water is the best protection and to run cooler in the summer.
(warm weather climates only!)

Can be used / mixed with antifreeze in colder areas.

Will prevent the white junk you see around the inside of radiator tubes (which is silicate drop-out from anti-freeze).

Prevents electrolysis and corrosion.

Provides better heat transfer, as well as the surficant for breaking down surface tension, and cleans the cooling system every time the engine is running.

Balances the PH in the cooling system.



It does not mix with other coolants very well.

If the car came with it, it should be okay, otherwise, converting to it is bad news.

You’ll never get it all out of your system (in the future) should you need to.

If you do use it, you should add RMI to keep your radiator unclogged.



WaterWetter and other similar brands lack enough lubricant and may allow rust unless re-added frequently in a daily driven vehicle.
That means short water pump life.

Tends to be corrosive/acidic and produces electrolysis.

It will erode the solder in the radiator unless another additive is used.



Grab the garden hose…
that’s missing the male end…
because you ran over it with your Buick Regal…
and squished it.

It’ll hook right up to the heater core exit.


As you can see, there’s a variety of different methods as to what kind of Coolant Antifreeze to put in your Buick Grand National (or other Turbo Regal).

What you use depends on where you live.
Choose one style and then stick to it forever.


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