Best Mineral Oil for Old R-12 System?

JHZR2 on Sat July 20, 2013 12:17 AM

Year: 1982
Make: Mercedes
Model: 300CD
Refrigerant Type: R-12

Hello,

My 82 Mercedes has sat for a few years now and the AC will not come on. I have R-134a gauges, but I am hesitant to attach them to the R-12 system in my old MB and then use them again in a 134a system - so Im waiting on an R-12 gauge to come in.

Assuming it is low charge from sitting for so long, my intent is to replace the schrader valves on high and low sides, and then replace the receiver dryer and its o-rings.

Since Ill be replacing that item, and it appears to be where oil accumulates, Ill need to refresh some oil. I believe it is mineral oil in there, the system has not been converted from R-12.

So, what is the best brand of mineral oil out there for auto AC? Searching hasnt shown a lot. Does it really matter? Would there by any reason why I would consider adding POE oil (one that says it is compatible with R-12) in with the remnant mineral oil?

Thanks!

webbch on Sat July 20, 2013 1:09 AM

Site sponsor sells it on his site. That's where I got mine. I think you can still find it at napa as well. I haven't heard any brand wars on mineral oil on this or other forums.

You _can_ purge the hoses of R-134a before attaching to the R-12 system. Better yet, flush them. However, the best option is like you're doing...have a second gauge set that you use only for R-12 systems.

For R-12 systems, I like to do a vacuum test AND pressure test before charging with my "precious" R-12. The stuff is getting too spendy to replace over a leak that could've been identified and fixed first.

WyrTwister on Sat July 20, 2013 6:49 AM

Quote
Originally posted by: JHZR2
Hello,

My 82 Mercedes has sat for a few years now and the AC will not come on. I have R-134a gauges, but I am hesitant to attach them to the R-12 system in my old MB and then use them again in a 134a system - so Im waiting on an R-12 gauge to come in.

Assuming it is low charge from sitting for so long, my intent is to replace the schrader valves on high and low sides, and then replace the receiver dryer and its o-rings.

Since Ill be replacing that item, and it appears to be where oil accumulates, Ill need to refresh some oil. I believe it is mineral oil in there, the system has not been converted from R-12.

So, what is the best brand of mineral oil out there for auto AC? Searching hasnt shown a lot. Does it really matter? Would there by any reason why I would consider adding POE oil (one that says it is compatible with R-12) in with the remnant mineral oil?

Thanks!

I bought a quart at NAPA to lube seals and O-rings . They were the only place I could find it .

God bless
Wyr

PS Does anyone know if this is the same mineral oil used in R-22 residential units ?

JHZR2 on Sat July 20, 2013 11:00 AM

Thanks! It was my intent to use the site sponsor unless there was some brand advantage of one type over another. I dont know enough about it - given an airless sytem, are there even any additives in mineral oils used in AC systems? For all I know it could be the same as what you get at the pharmacy.

I appreciate the insight!

wptski on Sat July 20, 2013 12:38 PM

I've heard that it's highly refined and so pure it can be used to wash refrigerant from your eyes.

Dougflas on Sat July 20, 2013 12:49 PM

The oil is different. Automotive was 525 while R22 used 300

Edited: Sat July 20, 2013 at 12:52 PM by Dougflas

Leggie on Wed July 24, 2013 7:32 AM

I've read that specified viscosity can vary quite a bit between auto systems. Even with same model/year, it can depend on compressor type.