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Rotax 912 Coolant

skippydiesel

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#1
Hi All -

Rotax used recommend Castrol Anti-Freeze Anti- Boil Concentrate at 50:50 . Rotax viewed this concentrate as being a formulation "low in silicate and free of nitrate".

I have run out of the supply that I had on hand and now find that the above product is not being stocked by my supplier.

Questions;

1. What is the name of the current Castrol substitute for the above?
2. What concentrate are most Rotax 912 drivers using?
3. I have access to a supply of reverse osmosis (RO) water - is this okay to use?
4. Or should I go out and purchase deionised water?
5. Or Distilled water?
 

facthunter

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#2
That product is no longer made. I use Pureau mixed with coolant. The coolant of your choice. It's like having a degree in organic chemistry to work out what to use. Water cools better than glycol so use minimum % that works . Keep the makers (coolant) mix ratio as a minimum as below that it doesn't do the right thing corrosion wise. Some coolants use a test strip to check when to change or add concentrate. Nev
 

alf jessup

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#4
I just use Evans NPG and have so for the last 10 1/2 years with my trike (6)and the Tecnam (4 1/2) (912 4 strokes)
Never an issue and never a problem and best of all never have to change it
 

onetrack

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#5
If your heart is set on Castrol products (which I have little time for), then the current Castrol coolant additive is Castrol Radicool.

It's available from Sparesbox on eBay or directly from the Sparesbox website.

Castrol Radicool Coolant Concentrate 2.5L 3 Box 3377732-BOX3

Radicool is a current-technology low silicate, OAT (Organic Acid Technology) coolant additive, and its "mixture of monoethylene glycol and selected chemical agents, contains no nitrites, amines or phosphates".

Keep in mind, it is an additive with a need to mix 50-50 with distilled water - and it's only good for 4 years (there's some conflicting info here - I also found a Castrol specification sheet that says 3 yrs lifespan).

Never mix coolant brands, types or colours - always flush the system thoroughly before coolant replacement.

Personally, I've yet to find anything to beat genuine Toyota long-life premixed coolant. It's good for 8 years - and it's also low-silicate, OAT, and nitrite, amine and phosphate-free.

EDIT - I just noticed that the Castrol Anti-Freeze, Anti-Boil product is also still available on eBay. So either it is not obsolete, or someone is selling old stock.

Castrol Coolant Concentrate 2.5L x 3 Packs each makes 7.5 L anti-freeze/boil | eBay
 
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Downunder

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#6
I'm about to move to Radicool.
I'm told it is more suitable for aussie conditions where as some others are more "european" in their design.
Meaning a larger focus on cold temps (anti-freeze) rather than our hotter summer temps found here.....
One Rotax user told me he dropped 5 deg c from the previous brand which is what I'm looking for.

Radicool can be purchased premixed....no need for water.
Castrol Radicool Coolant Premix 5L 3377804 | eBay

Evans coolant is no longer recommended by Rotax. Not saying you should change from it, but I wouldn't change to it.
 

alf jessup

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#8
I'm about to move to Radicool.
I'm told it is more suitable for aussie conditions where as some others are more "european" in their design.
Meaning a larger focus on cold temps (anti-freeze) rather than our hotter summer temps found here.....
One Rotax user told me he dropped 5 deg c from the previous brand which is what I'm looking for.

Radicool can be purchased premixed....no need for water.
Castrol Radicool Coolant Premix 5L 3377804 | eBay

Evans coolant is no longer recommended by Rotax. Not saying you should change from it, but I wouldn't change to it.
Downunder
I believe it is not recommend for the later model 912 engines with the redesigned heads
Rotax years back advised not to use 50/50 mix and switch to Evans which I did
I personally think they recommend whoever is paying them the most to run their brand of coolant in their engines
I have had not one ounce of trouble in the combined 1100 hrs of use with 4 stroke Rotax engines using Evans and I'm not about to change at this point in time

Cheers Alf
 

Downunder

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#11
Yes, you're correct Alf as per the SI. New heads only. However I don;t know the age of Skippy's engine so was just putting the info out there.
When did they start with them heads? 2013? Must be starting to get a few about....
My friends CT runs very nicely with the evans...

Some really good info on the last page of the SI...... all Rotax owners should be aware of...
 

facthunter

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#12
There's been extra information out on Evans. The engine does run hotter with it as it doesn't move heat as well as water but can safely run hotter without steam hotspots. Check that it's really suitable for your particular application..The product I was referring to was the 400 mm concentrate Castrol cans that I used for years. 3 did 15 litres. Caltex made an equivalent and I bought a lot of those in bulk but again that product has been superseded. They are not really an antifreeze as they don't have enough glycol % to have much effect inthat regard. Glycol gives anti freeze function but has it's own problems. It leaks out of the tiniest places and doesn't help removing heat as well as water by itself. It can also go off and cause corrosion. As said, DONT MIX Brands or types. It's a dog's breakfast this area now. If you mix your own use pure water with no mineral content in the right ratio as specified on the product. Less than specified may render the effect nullified. It's also expensive. If you look at the cost of the chemicals used to make this stuff you will see how you are being ripped off. Bit like all "oil" products for automotive use today. Nev
 

alf jessup

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#14
Nev
I like that the Evans makes it run warmer
My heads now run at 95 and the oil came up 10 deg as well
Gained 30 deg on the heads from the glycol mix which used to run at about 65
Never had the heads or oil temp ever go out of the green even on a 40 deg day on a prolonged climb to altitude

Alf
 

skippydiesel

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#15
OKAY - done a bit more research :

Castrol advise:
"Radicool Concentrate" is a direct replacement for "Anti-Freeze Anti-Boil (AFAB) Concentrate"
Both Radicool & AFAB contain low (?) levels of silicate and use nitrites as an anti corrosion agent.
Further - the nil nitrite specification is not out of concern for the engine but a European concern for nitrites entering the environment ie a pollution issue.
(My words - for those that insist on the nitrite free coolant -)
Castrol have a nil nitrit coolant available "Radicool NF" specified for European cars (eg Mercedes). The NF may be hard to find and come in a larger minimum quantity than you want.

Bert Flood advise:
"Radicool Concentrate" is a direct replacement for "Anti-Freeze Anti-Boil (AFAB) Concentrate"


My own feelings on coolant choices recommended by Rotax:

Evans

I have never used Evans - however Rotax advise a lower thermal efficiency than glycol mix and on no account can it be mixed/contaminated with even a small amount of water/glycol coolant.
I also believe Evans to be considerably more expensive than conventional glycol coolant.
Its main benefit seems to be indefinite in service life.
Sooooo -
A change to Evans would require a cooling system flush to remove all traces of glycol/water coolant.
I have to change rubber every 5 years, this will inevitably result in some loss of coolant and the danger of contaminating the saved coolant.
Purchasing top up coolant and filtering of old coolant seem to be likely scenarios - Cost Mess & Extra Time
Loss of coolant while away on a trip would be a serious problem - cannot top up with glycol/water.
On balance I prefer to stick with the Castrol coolant that appears to have given my engine good service for nearly 800hrs/17 years.

Castrol Concentrate
(and any other Rotax compliant glycol coolant)
I use it at the recommended 50:50 ratio, as I have always done in my land based vehicles.
I believe this gives me:
A cost effective coolant
That gives good increased boiling point and anti freezing (not so important in our climate) qualities ie good thermal characteristics.
Anti corrosion qualities to protect the internals of the cooling system.
Lubrication of seals
Maximum time of in service life (see manufacturer's recommendation)
Is widely available, should a top up be required (touch wood - never happened).

I would not use a pre mix as they are usually at a lower than 50:50 ratio nor would I mix the concentrate at less than the Rotax recommended ratio as I feel that some of the benefits listed above would be diminished.
 

onetrack

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#16
You've nailed all the pertinent points very well, with a great deal of thought. The point about being able to refill/top-up in case of coolant loss, when a long way from home, is very important.
The latest OAT coolant technology is very good. The important thing is taking notice of the manufacturers advice, because they alone know the precise composition of the alloys they use.
There are a multitude of alloys utilised today, and with multiple components, often utilising different metals, electrolysis is always ready to rear its ugly head.
There are also recommendations from coolant manufacturers to check for stray electrical discharge through the radiator, which can accelerate electrolysis caused by dissimilar metals in contact with coolant.