I’ve had my Eunos (mk1, 1800) for 8 years and never changed the coolant. Idly looking at Honest Johns review of new MX5 the other day he says it needs special (and expensive) mazda coolant. Any thoughts on this, perhaps it only applies to more modern engines?
I believe the new ones use red longlife coolant. Your Eunos was designed for the blue or green 2-year stuff. Mazda Super Coolant (green) is pre-mixed and not all that expensive; the main problem is that it comes in 5 litre bottles, and you need 6 litres.
Eight years is flirting with head gasket failure. You should change it every two years to avoid internal corrosion; the passivating additives don’t last longer than that.
Blue antifreeze contains silicates. Japanese engines require silicate-free antifreeze, therefore use only green or red HOAT/OAT silicate free antifreeze.
http://universallubes.com/images/uploads/0703-1-AF-Rainbow.pdf
Thanks for the clarification.
I use the Mazda green coolant in mine. I put Mobil OAT coolant (silicate free) in a Merlot back in 2006 - it’s almost due for a change now. We spent a lot of time flushing out the remains of the green stuff from the system and changed the thermostat at the same time (this can make an amazing difference to how quickly the car warms up from cold, if your old stat was getting a bit leaky).
http://www.mobil.co.uk/uk-english/lcw/Files/Car_Care.pdf
The word is that the two-year stuff is better for the B engine if you can handle the more frequent changes; the passivating additives don’t last as long but are more powerful. The five-year coolants have slower-acting passivators.
Judging by what you’re both saying, I probably don’t need to change the coolant in my car this year if it was done last year? Is that correct?
I was thinking about freshening it before winter, but if it’s one job I don’t absolutely have to do I’ll drop it further down the list.
Input much appreciated…
I’m not aware of any modern coolants that need changing annually.
Thanks for the clarification. I’m no mechanic. As you can tell…
Whatever you do, don’t be suckered into dropping in some Redline Waterwetter on top of the antifreeze; it tends to react with the antifreeze, to form globular particles. Its really designed to be mixed in with water only. I suppose this might constitute a coolant that needs changing annually.
Sorry to be a bit dense here, but how often should I change my coolant on my NA (91)?
Gary, have a look here
http://www.mx5oc.co.uk/forum/files/folders/service_sheets/entry2998.aspx
Robbie uploaded some servicing schedules a while ago. Quick answer every two years
Thanks Geoff
This is all very confusing. Can someone advise me on what Antifreeze to use in my 2003 Mk2.5?
MX5 parts say a standard Mobil antifreeze but the picture they use is Mobil Advanced which is a different animal entirely. It seems the choice of different Antifreeze types is just as bad these days as the plethora of Engine Oil types,
See this. I’d advise you get some of the Super Coolant and use that in your car.
Robie, I can’t find this Super Coolant on the Internet anywhere so I assume it’s only available from Mazda main dealers?
Do you know the spec of it? ie with/without Phosphates, Silicates, OAT which are metioned above. etc. There must be an alternative similar spec stuff by some other manufacturer surely.
Sorry, no idea of the spec. Any ethylene-glycol anti freeze will be fine, the important thing is to only mix it with distilled water if you buy it as a concentrate.
Hooray - I finally got a 5 litre can of this Mazda green Super Coolant stuff but to my disgust I find the car takes 6 litres and you can’t buy a 1 litre bottle. Ha Ha Ha Ha
Anybody think it would be wrong to use a bit of the old stuff to get up to the Max mark?
Or won’t I need to, as others seem not to be able to get all the water out after flushing.
Who has practically done this - will the 5 litres fill to the max mark? Don’t want to buy another 5 litres just for 1 litre. (£14)
I’ve never managed to get all 6 litres out/in. But I wouldn’t mix coolants if I were you. Top up with water won’t kill it, but ideally you’d get some more and save it for next time…after 5 services you’ll be back square. 
call me old fashioned but over the last 8 yrs, I have just drained a bit of fluid out & topped up with garage antifreeze to the right strength according to the halfords tester.
the car lives on the drive so it’s survived a lot of cold nights over the years. the only time all the fluid was changed was last november when i did an engine change.
That’s not old fashioned…just wrong. It’s not the anti-freeze that’s the problem, but the various types of corrosion inhibitors that a) don’t like being mixed and b) get used up and stop working after a couple of years. Any old antifreeze will stop the jacket bursting on a cold night…it’s corrosion that will see the end of an engine.
A coolant tester only tests the antifreeze concentration, nothing else.