Denso Oil 8 - HFC-134a oil

[ssbtech]

Can't believe search turned up nothing on this.

FSM states not to mix PAG oils for the AC system and specifies "Denso Oil 8", which of course I can't find anywhere.  Denso Oil 8 is a PAG46 oil. 

Is the warning against mixing oils based on mixing oils for different refrigerant types, or is it unacceptable to mix different oils of the same type, i.e. Denso Oil 8 already in the system with added PAG46 from a different brand?

I'll be replacing my evaporator soon, the system has already been professionally evacuated.  I suppose I could transfer the oil from the old evaporator to the new one but I'd prefer fresh oil.

 

Thanks.

[KZJonny]

I just did a new evaporator/compressor in my car, and just used the PAG46 oil supplied by Rockauto. So far so good, and the compressor seems happy enough. (I think the warning would be against mixing with another grade, like PAG 20 which is for a different type of compressor, etc....)

I seriously doubt there is any secret sauce to the Denso Oil 8 aside from them insisting on it to sell more of their own product.

 

Do you use exclusively Subaru branded motor oil as probably suggested by SOA somewhere? 

Edited August 11, 2023 by KZJonny

[ssbtech]

There's actually quite a bit of difference between the chemical structure of compressor oils.  This is less of a Subaru recommendation and more of a Denso recommendation for their compressors.

 

https://docs.lib.purdue.edu/cgi/viewcontent.cgi?referer=&httpsredir=1&article=2250&context=icec#:~:text=The single end capped P,performance and lubrication was observed.

https://automotivetechinfo.com/wp-content/uploads/2018/11/AC-System-Lubricant.pdf

 I did end up finding a can of Denso 8 oil which I ultimately didn't need as nothing dribbled out of the old evaporator

 

 

[KZJonny]

Convincing evidence for the use of diether PAG oil in that Purdue link. I will remember to check on the manufacture of whatever oil I uses in future when working on A/C systesm.

Hell, I'll do some digging on what I put into my system when I rebuilt it last month. But I am also quite sure that Denso 8 won't be the only high quality oil available out there, or at least I hope so since it was 100% not available to me when I tried to source some.

[ssbtech]

I found mine here: https://www.abilenemachine.com/denso-nd8-pag-oil-46v-amx10272

 

You said you replaced your compressor - new unit?  I thought they came pre-filled with the appropriate quantity.

 

[KZJonny]

Haha, well, yes. That is technically 'available to me', but for $31 USD and then another $28USD to get it shipped to me, then also maybe customs on top of that.....

 

New evaporator was actually new. Sealed and N2 purged, and with a new dessicant charge. The compressor was "new" from a parts car via a bin in my basement, so it was not only entirely free of oil, it was a little rusty and in need of a thorough cleaning. However, total cost = $0. If it had been a genuine ND rebuild, I would be content to use the oil that came in it, but I've also been warned that if you're buying a budget reman, you'll get what you pay for.

Maybe I should have been more specific than "any old PAG oil, they are all the same". I did at least get the more expensive, full synthetic stuff, tho probably all of it is synthetic, really. I don't think there is an awful of diether methyl and ethyl chain fractions from natural sources anyway. I guess you'd start probably start with methane and build them up to do it the "easy way".

Edited August 11, 2023 by KZJonny

[ssbtech]

Heh.  I too am in Canada   Just didn't want to take a chance mixing oils in a system that I can't easily drain and fill myself.  I don't have AC tools. 

The evaporator and expansion valve were a fun replacement.  Didn't have to pull the dash though.

Cheers.

 

[KZJonny]

Oh crap, I’m a dummy. I replaced the condenser, not the evaporator. Much less work involved. Sorry.

I wrote Supercool to ask if their PAG oils are diether just to find out.

I did get myself an Amazon vacuum pump and gauge set to evacuate and correctly refill the system tho. Works well, and I did a friends car as well that had zero refrigerant in it due to some aged out o-rings. For me it was worth it, ended up spending much less on the tools than paying someone to do the work x2.

I’ve got access to N2 through work and Argon from my TIG tho too, so pressure testing cost $0.