Best coolant for a 1995 Mazda Miata

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Le_bow_ski

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Greetings all. I'm planning on replacing the coolant in my 1995 Mazda Miata and I'm looking to those more experienced to help me decide which one is best. At present I change the coolant every 3 years or 30k miles or so, and the car now has 30k miles on it.

The 1.8 liter motor has a cast iron block and aluminum head. I believe the coolant in it is Prestone All Makes All Models (a Dexclone?). While I don't have any major negative issues with the Prestone it does leave a brown coating on the inside of the coolant reserve bottle, which is vented to atmosphere. Perhaps an alternative coolant will keep the reserve bottle, and the cooling system, cleaner.

My research suggests a G-5 coolant might be a suitable choice, but I'd like to hear what you have to say. My primary goal is keeping my 18 year old heater core healthy, as replacement of that core usually requires removing the car's dash. After that, keeping the water pump and remainder of the cooling system healthy is next in line, followed by extended change intervals, and lastly by cost. I guess I'm just looking for the best coolant for my soon to be vintage Miata.

Any suggestions?
 
I assume it old green from the factory? If so then G-05 is a fine choice, Zerex G-05, NAPA has it.

If it had an extended life coolant, then I would go with Zerex Asian.

The difference being the Zerex Asian is a no silicon and G-05 is low silicon. Silicon by the way is good as long as your water pump is designed for it.

I have used G-05 in my 2 current vehicles as well as 94 Camry and 93 Suburban.

You will need to do a decent job of flushing the current coolant out with water or distilled water.
 
I'll check and get back when I get home. But I'm also thinking coolant technology has changed quite a bit in the last 18 years, and that a coolant taking advantage of that new technology might be an improvement.
 
Originally Posted By: Donald
I assume it old green from the factory? If so then G-05 is a fine choice, Zerex G-05, NAPA has it.

If it had an extended life coolant, then I would go with Zerex Asian.
Why the different recommendation depending on the previous coolant? Whatever I use I will thoroughly flush the oil coolant out and use distilled water with the new.
 
Originally Posted By: Le_bow_ski
Originally Posted By: Donald
I assume it old green from the factory? If so then G-05 is a fine choice, Zerex G-05, NAPA has it.

If it had an extended life coolant, then I would go with Zerex Asian.
Why the different recommendation depending on the previous coolant? Whatever I use I will thoroughly flush the oil coolant out and use distilled water with the new.


Not the previous coolant, but the original. If it has a water pump designed for no silicon like most new Asian cars then use a new technology coolant like Zerex Asian. If it had old green which was silicon or low silicon, then G-05.
 
Originally Posted By: Donald
Not the previous coolant, but the original. If it has a water pump designed for no silicon like most new Asian cars then use a new technology coolant like Zerex Asian. If it had old green which was silicon or low silicon, then G-05.
Gotch ya, and thanks. I'll have to confirm, but I believe the original was an ethylene glycol based coolant, based on that being the predominant coolant type two decades ago.
 
Almost all coolant is ethylene glycol based coolant except a few low toxic ones. Its the chemistry on top of ethylene glycol we are talking about, like OAT or HOAT, etc.
 
Originally Posted By: Donald
...Its the chemistry on top of ethylene glycol we are talking about, like OAT or HOAT, etc.
And that's exactly where you loose me. But if I understand you correctly the G-05 is the more likely candidate given what we know now. Change it often enough so the silicates don't drop out and I should be good to go. I very much doubt that the '95 Miatas came with an extended change coolant.
 
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It probably came with the conventional silicate green coolant. You now have a dex clone in there so you really want to get all of that out with a good flush .

G05 works in anything. I'm using it in my Buick.

If you have trouble finding Zerex G05 you could always go back to conventional green. The auto parts store in house brands of coolant are all about the same from a major manufacturer.

I got my g05 off Amazon, but only be ause I don't have a Napa anymore since it closed.
 
Checked the owner's manual; all it says is to use ethylene glycol based coolant and to replace it every 30k miles. So G-05 it is. Thanks everyone, I appreciate all of your help.
 
Should work well. My truck has had G-05 in it since new. I have done drain and fills with John Deere Coolgard II in the last couple of years, but it's closely related to G-05 and there's still a lot of G-05 in the system. The cooling system is spotless at nearly 150K miles with no flushes ever done. Never had a t-stat go bad, never replaced the water pump. The reservoir is totally clean, no grime at all. Heater core is original and the heat is HOT, radiator was only replaced due to a tank cracking because of a wreck. The old one was spotless inside at the top and bottom. It has leaked some from the water neck since about 70K miles, which seems to be the result of a porous casting, and unrelated to the coolant. When I have had it off to chase the leak, I have gotten a good look in the intake manifold. The cooling system is truly spotless. Hoses are original except for one heater hose that cracked at a plastic t, also unrelated to the coolant. In cooling systems where silicates are okay, I think G-05 and similar coolants are the way to go.
 
Originally Posted By: 01rangerxl
Should work well. My truck has had G-05 in it since new. I have done drain and fills with John Deere Coolgard II in the last couple of years, but it's closely related to G-05 and there's still a lot of G-05 in the system. The cooling system is spotless at nearly 150K miles with no flushes ever done. Never had a t-stat go bad, never replaced the water pump. The reservoir is totally clean, no grime at all. Heater core is original and the heat is HOT, radiator was only replaced due to a tank cracking because of a wreck. The old one was spotless inside at the top and bottom. It has leaked some from the water neck since about 70K miles, which seems to be the result of a porous casting, and unrelated to the coolant. When I have had it off to chase the leak, I have gotten a good look in the intake manifold. The cooling system is truly spotless. Hoses are original except for one heater hose that cracked at a plastic t, also unrelated to the coolant. In cooling systems where silicates are okay, I think G-05 and similar coolants are the way to go.
Thanks for the review. This is the outcome I'm looking for.
 
I would be using the OEM stuff, odds are it is a non-silicate coolant that has phosphates. Japanese car companies use water pumps that don't always last when silicate coolants are used.
 
Originally Posted By: artificialist
I would be using the OEM stuff, odds are it is a non-silicate coolant that has phosphates. Japanese car companies use water pumps that don't always last when silicate coolants are used.
I think that's correct now, but not so 19 years ago when the car was manufactured.
 
Originally Posted By: Le_bow_ski
Originally Posted By: artificialist
I would be using the OEM stuff, odds are it is a non-silicate coolant that has phosphates. Japanese car companies use water pumps that don't always last when silicate coolants are used.
I think that's correct now, but not so 19 years ago when the car was manufactured.

It happened to a 1994 Mitsubishi Expo and 1995 Honda Accord, both cars driven by my parents, and we all thought that is coolant was green, it was the same stuff.

So 19 years ago, Japanese car companies were using non-silicate coolants.

Toyota was a little different, using no phosphates, but they also used no silicates.
 
Originally Posted By: artificialist
Originally Posted By: Le_bow_ski
Originally Posted By: artificialist
I would be using the OEM stuff, odds are it is a non-silicate coolant that has phosphates. Japanese car companies use water pumps that don't always last when silicate coolants are used.
I think that's correct now, but not so 19 years ago when the car was manufactured.

It happened to a 1994 Mitsubishi Expo and 1995 Honda Accord, both cars driven by my parents, and we all thought that is coolant was green, it was the same stuff.

So 19 years ago, Japanese car companies were using non-silicate coolants.

Toyota was a little different, using no phosphates, but they also used no silicates.
Thanks for the followup info; I'll look into it more closely.
 
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