View Full Version : Mineral, AB, POE, PAG. When to use what oil?

23-10-2003, 11:20 AM
I came to this question when I say Herefishy mention an oil change to alkylbenzene to run an R12 compressor with R404a. I thought an oil change to POE was the way to go.

The application of mineral oil is fairly straightforward (is it?). It will work with hydrocarbon refrigerants, R22, and the zillion 'compatible' drop-ins for R12 and R22.

But then we have POE, AB and PAG. R134a, R404a, R507, R410a, R407, they all run well with POE. But why do automotive airconditioning systems use PAG instead of POE? When would one consider AB instead of POE? What are the specific advantages and disadvantages of each lubricant?

23-10-2003, 03:31 PM
Hi DaBit, I could be wrong.. let me check.... I mis-spoke :(

POE is the recommended lubricant for 404A...

23-10-2003, 03:42 PM
But still, the question remains.

What are each lubricants specific advantages and disadvantages. When to choose what lubricant? Why PAG in automotive R134a apps and POE in domestic R134a apps?

23-10-2003, 04:53 PM
pgs. 4 & 5 give some info..



The following delineates between "miscibility" and "solubility". It is stated that refrigerant miscibility is helpful, but not necessarily essential essential for proper operation.... I guess I have misused the term (as a blanket statement for "incompatable".

pg. 5



Anyway, I think your're looking for some explanation in the realm of an H-bond, or something at the molecular level to explain the applications, right?

Good subject.

Frig Pig
23-10-2003, 10:59 PM
hydro aswell. poe is a 1000 times more of an h2o absorbant than mineral oil and alky. pag is 1000 times more than poe. floc point is critaical too. waxing is a prob. w/ mineral but not w/ poe & pag. poe is 100% missable until saturation above 85 degrees F i think therfore prob the best for most apps. i can't recall why pag is used in auto a/c. it's really bugging me now. somebody?

23-10-2003, 11:29 PM
POE Oil 45+ for 5 litres, Alkyl-Benzene Oil 20+ for 5 Litres,
Mineral Oil 13+ for 5 litres - see where i am coming from.

POE obviously a far superior oil but why use it on a system/gas that is ok with AB oils.

Most new units requie POE buy on older ones why waste money on the oil when AB & mineral has done the job ok for years.

24-10-2003, 07:29 AM
Here are 2 possible reasons why PAG is used instead of POE in automotive:

1) PAG may be more compatable with the seals and 'rubber' parts than POE

2) It's all a money thing - why use ACME fittings on R134A bottles instead of the regular fittings (at least here in the USA)? It's the same refrigerant, isn't it?

Karl Hofmann
24-10-2003, 08:12 AM
The issue of PAG over POE has been discussed to death over on the ACKits web site. I think that we all agreed that POE was the superior lubricant for automotive work and that when retrofitting POE is usually the lube of choice in the US. As to why PAG is used by the manufacturers.....Erm well, nothing conclusive there! My feelings are that if the lubricant absorbs more water, then the manufacturers have a stronger argument to replace the reciever drier at a ridiculous price (Some can cost up to 180) Like everything else involving automotive I suspect that it is a scam.:mad:

24-10-2003, 08:31 AM
It is good to know that I am not the only one confused.

I visited our local HVAC school the other day and the instructor was saying that they have started to use ERG1000 (www.erg1000.com) on their R134a coke machines with a good deal of success. This PAO oil does not suck up the moisture like POE and PAG, but neither is it miscible with R134a. The scrapped coke machines are regularly disassembled and rebuilt by the apprentices and POE oils would quickly become water logged.

Ammonia plants also use oil that is not miscible with the refrigerant.

The ERG1000 PAO oil has been on the market for a good few years now, and I have not heard of any horror stories. But I still don't understand how it works.

Karl Hofmann
24-10-2003, 09:25 AM
My problem with PAO is if it is not miscible with R134a (the manufacturers say that the oil is "dragged" round by the refrigerant), then why not stick with Mineral oil?

27-10-2003, 10:26 AM
Thus, POE is still the best choice for all 'modern' HFC refrigerants like R134a, R404a, R507, R410A, R407C, etc. Other oils are used to reduce costs.

Would that be a good conclusion?

27-10-2003, 05:38 PM
The following website shows various refrigerants and the oils they are compatible with:


28-10-2003, 10:02 AM
I am aware of that site, but it doesn't mention why oil A is used in application X, and oil B in application Y.

Karl Hofmann
05-12-2003, 10:42 AM
No one will say exactly why PAG was selected for automotive ac, but the hose fitted to R134a systems has a high density liner which is the barrier to reduce leakage. I would worry more about the leakage from joints that are sealed with O rings , lousy compressor shaft seals and corrosion of aluminium components (Especially when the manufacturer uses steel brackets and clips on these components)

05-12-2003, 03:23 PM
Hi DaBit,

I`m affraid there is no straight forward answer to your quwestion.
I belive it`s all come down to money. POE is expencive but good oil i guess for most new refrigerants. you can not keep it for a long time and you have to change it more frequent.
is this the type of oil we are looking for? not realy. but for some reason you can not use mineral oil with new refrigerants.
PAG was selected from a reason which is beyond us.

for the sport, try contact the oil manufacturers and see if they will answer you.
Karl Hofmann is right and I think too that you are chasing the wind.


05-12-2003, 03:48 PM
Oh, I was just curious. There are many different sorts of oil, and when viewed with my technical eyes, one must have an advantage over another in a certain application to chose it. That is why I asked the question since I assumed that you professionals could tell me.

Now it seems that oils are chosen only partly because of technical reasons, and more because of political/economic reasons. Which does not interest me that much.