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Using oil for the coolant system for a Rotax


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I was talking with a friend of mine the other day and he tells me one of the flying schools sort of locally around here use "oil" in the cooling system on their Rotax powered training aircraft. I have never heard of this apparently the engines run 7 deg warmer but no electrolysis issues when doing this. The discussion started about what I am going to use in my Savannah I haven't decided yet but was probably going to use 50/50 water/glycol.

 

Never heard of using oil for that sort of cooling how common is this?

 

Mark

 

 

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Oil has nothing like the capacity to transfer heat compared with water. Brine is even better, but too corrosive to be used in engines. Glycol os not as good as water ( at transferring heat) but has a higher boiling and a lower freezing point. This permits the engine to operate at a higher temp without pressurising the system excessively.

 

I'm sure Rotax would not approve the use of oil as a coolant. There is a waterless coolant available that some use but the name of it eludes me at the moment.

 

Oil is used to cool some motors internally but not in the jackets. The Suzuki Katana and some BMW's to name a couple, but all motors to some extent rely on the oil to cool bearings, pistons etc. Nev

 

 

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Guest Andys@coffs

So I struggle to understand how this would be at all legal. If its a training aircraft (in Aus and within RAA) then it has to be 24 registered and operated IAW manufacturers instructions. I challenge to have someone show me POH or failing that in an engine manufacturers installation and usage manual, that will endorse this approach, and even if they can (engine manual) , unless the Aircraft manufacturer sends it to you that way from the factory then the point still stands doesnt it?........

 

Andy

 

 

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I was talking with a friend of mine the other day and he tells me one of the flying schools sort of locally around here use "oil" in the cooling system on their Rotax powered training aircraft. I have never heard of this apparently the engines run 7 deg warmer but no electrolysis issues when doing this. The discussion started about what I am going to use in my Savannah I haven't decided yet but was probably going to use 50/50 water/glycol.Never heard of using oil for that sort of cooling how common is this?

Mark

There is a service instruction out from Rotax, Selection of suitable operating fluids, SI-912-016 R4, dated 31 AUG 11, and posted 14 SEP 11 on http://www.auf.asn.au/

 

 

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Guest Andys@coffs

So, to use that tired old analogy "oils aint oils" Perhaps, after reading the link Wayne provided the "oil" that is being discussed is the waterless coolant which isnt an oil as such, rather, according to the document, "Propylene Glycol"

 

Andy

 

 

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Generally if oil gets in the cooling system of an agricultural, or motor vehicle it will run hotter. Oil retains heat much longer than water as Nev mentioned. (hence the reason they use it for cooking!)

 

 

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Lots of info on American auto conversion websites. The coolant referred to is Evans waterless coolant. It is totally non-compatible with water -based coolants, and in my opinion, the jury is out as to its effectiveness and the need to use anything but water with an anti-freeze, antiboil additive. I have always used a good quality auto coolant concentrate, mixed 50-50 with clean rainwater out of a plastic tank. Good for 4 years before replacement.

 

 

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Dont forget, the Rotax 912 is about 40% oil cooled already! oil in the tank looses heat rapidly as well as the oil cooler itself, our savvy has the cooler about 1/3 covered in summer, and about 2/3 rds covered to maintain oil temp at around 95DegC.

 

the other coolant is Evans waterless coolant, though a similar product, well, its identical, glycol propylene or whatever it is, made for racing motorcycle engines, its far cheaper than evans.

 

 

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  • 4 weeks later...

But none of these are oils. Oil will not remove heat anywhere near as well as water or the products mentioned. As well the hoses would not last long. IF you get even a small amount of oil in the coolant they deteriorate rapidly.

 

Any one who has done heat treating will know you get different results quenching in oil than with water or nitrate salts...Nev

 

 

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