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Suitable Operating Fluids for Rotax 912 series

WingedFrog

WingedFrog

Well Known Member
I was struggling to find what kind of coolant I should put in my 912 ULS, looked at Rotax manuals, had different advices at the airport, did some VAF research and then I found this gem form Rotax: SI-912-016 R4
Problem solved (and many more down the road)!
 
I am using Evans NPG in my Viking, and see that Rotax likes it as well. It is generally called "racing coolant" since it won't boil or form bubbles against the metal of the engine.
 
DonFromTX said:
I am using Evans NPG in my Viking, and see that Rotax likes it as well. It is generally called "racing coolant" since it won't boil or form bubbles against the metal of the engine.
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For the Rotax, Evans is approved but not specifically recommended.

It has a couple of down sides...

It is much more expensive than using Dexcool.

It has a lower heat transfer coefficient compared to 50:50 conventional coolant. This means that CHT's and coolant temps will automatically be higher than they would be with the conventional coolant. So, the primary benefit is if a particular cooling system runs dangerously close to the boiling point, it gains some margin (but increases the overall operating temps).
 
In addition, what if you need a bit of coolant while away from home base? Can't add water to Evans.
 
Any Walmart premixed 50-50 name brand. Don't make things more complicated than they need to be.
 
Bill_H said:
Any Walmart premixed 50-50 name brand. Don't make things more complicated than they need to be.
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All right, I love buying my aviation stuff at Walmart! By the way, what quantity do I need, I was unable to find this in the Rotax doc (probably because it depends on the size of the expansion vase).
 
I don't know the exact quantity but if you buy a gallon, not pre-mixed, then mix it 50/50, you will have plenty left over.
 
Coolant capacity is 0.4 US Gallons per the Line Maint. Manual. If you do the mix, use distilled water. The premixed is very convenient.
 
It is definitely more expensive, but it is also a "forever" coolant", and is far more friendly to hoses and engine. I am however unable to find information to support your other complaints, do you have a reference?
http://www.evanscooling.com/

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rvbuilder2002 said:
For the Rotax, Evans is approved but not specifically recommended.

It has a couple of down sides...

It is much more expensive than using Dexcool.

It has a lower heat transfer coefficient compared to 50:50 conventional coolant. This means that CHT's and coolant temps will automatically be higher than they would be with the conventional coolant. So, the primary benefit is if a particular cooling system runs dangerously close to the boiling point, it gains some margin (but increases the overall operating temps).
Click to expand...
 
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Doesn't Rotax still recommend replacing coolant every two years?

Almost everyone I am aware of in the CT community has gone to dex. With the higher operating temperatures using Evans, I think Evans is better suited to airframes with a more open cowling where heat is less of an issue.

Just my thoughts. I have never used Evans and have no plans to do so.
 
I always went with DEXCOOL. Probably better than EG/PG type coolants from the perspective of longevity, cheaper than Evans and you can always add water in the field to top off. Never had CHTs close to where I would need Evans - Oil temps were hard to keep under 230, but CHTs were always good.

TODR
 
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