Do I need to add the 10ml of refrigerant oil when I replace the receiver drier?

[Theophilus]

The AC system on my 2003 Legacy Outback has been out of coolant for a long time, so I'm going to replace the receiver drier before I vacuum the whole system out.  My repair manual says that I should add 10ml of refrigerant oil to the system when I put in the new receiver drier, to replace what gets taken out in the old part.

 

Does anyone have an opinion about whether this is really necessary?  As far as I can tell, refrigerant oil is only sold in bottles of around 240ml.  It seems crazy that I would pay $10 for a bottle, use 1/24 of it, and throw the rest away.  If people were really regularly adding 10 ml at a time, wouldn't it be sold in smaller bottles?

 

If I really do need to add the oil, what weight do I get?  AutoZone sells three different weights of PAG oil, but there's nothing in the manual or on the sticker under the hood about that.  And where do I add it?  Does it matter whether I squirt it into the intake or outtake hole on the receiver drier?

 

Thanks for any guidance!

[1 Lucky Texan]

hmmmm....maybe check ebay for a smaller or partial bottle?


wonder if you can recover any from the old part?

also, there may be refrigerant cans with oil included - when you re-charge, maybe use one or 2 of those? (I have no idea how much oil might be in those cans, just seems like I have seen them for sale)

 

EDIT; yeah, this one has 2 oz of oil, and 2 of refrig. ;https://www.amazon.com/FJC-9144-PAG-Oil-Charge/dp/B0049MICUU/ref=sr_1_8?s=automotive&ie=UTF8&qid=1466005511&sr=1-8&keywords=r134a+with+oil

Edited June 15, 2016 by 1 Lucky Texan

[carfreak85]

You need to measure how much PAG oil is in the drier and top off the system with the same volume.  You don't hear about a lot of people doing this because most people leave A/C repair to pro mechanics who have the proper recovery tools.

 

There is an ideal ratio of oil to refrigerant.  The idea is that if you open the system and replace a component, you should replace the amount of oil lost from the system in that failed component.  If you use only 1% of your bottle of new PAG oil, so be it, that's all the system needs (Or just replace ALL the oil in your system). 

Edited June 15, 2016 by carfreak85

[Numbchux]

PAG 100. I followed the Service Manual suggestion for the parts I replaced.

[Theophilus]

hmmmm....maybe check ebay for a smaller or partial bottle?

 

 

yeah, this one has 2 oz of oil, and 2 of refrig. ;https://www.amazon.com/FJC-9144-PAG-Oil-Charge/dp/B0049MICUU/ref=sr_1_8?s=automotive&ie=UTF8&qid=1466005511&sr=1-8&keywords=r134a+with+oil

 

Hmm...  Thanks for the tip!  The R134a / PAG oil combo looks like a good option if someone needs to add a full 2 oz of oil, but it doesn't look like the right thing for the receiver drier replacement situation.

 

If I understand the math here correctly, 8 oz = 237 mL of refrigerant oil.  I only need 10 mL, so I'm looking for a way to add 1/3 oz.

 

The product at Amazon is a pressurized can, just like a regular can of R134a, and it has 2 oz of oil.  So, if I use that, I need to either A ) use the whole can, B ) use part of a can and then store it with a tap valve attached, or C ) use part of a can and then vent the rest of it into the atmosphere so I can get my tap valve back.  Option A would put way too much oil in the system.  And options B & C both would require me to use a very precise scale to measure out 1/3 oz.  Just doesn't look like the right way to go.

 

The whole thing would be so much simpler if a new receiver drier came with the right amount of oil already added.  Or maybe they could include a little plastic packet that you tear open to add 10 mL of oil.  Auto parts company executives, are you listening???  If my salad from Trader Joe's can come with a pre-measured packet of salad oil, why can't my receiver drier come with a similar packet of PAG oil?

Edited June 19, 2016 by Theophilus

[carfreak85]

They have no way of knowing if you need 10 ml or 100 ml, of PAG, that's why they don't include any. 

[1 Lucky Texan]

you can get an 8 oz bottle for less than $6 - free shipping - from ebay.

 

I haven't bothered looking for any small packets or partial bottles but - the above is an incredible deal.

[idosubaru]

it's not necessary, but get it done while you're going through it all.

the receiver/dryer and vacuuming aren't even necessary so you're way ahead of the game and necessary components. 

 

i'd install new orings, recharge it and run it 100,000 miles.  most Subaru A/C systems are simple and robust. 

[carfreak85]

I would review Subaru's service recommendations for working on the A/C system for your specific vehicle.  I write the service information for my employer and we REQUIRE the system be put under vacuum when serviced.  Cracking open the A/C system, unless you have the proper tools/gauges/what-have-yous, is best left to the pro mechanics.

[idosubaru]

I would review Subaru's service recommendations for working on the A/C system for your specific vehicle.  I write the service information for my employer and we REQUIRE the system be put under vacuum when serviced.  Cracking open the A/C system, unless you have the proper tools/gauges/what-have-yous, is best left to the pro mechanics.

 

That is the best approach and maybe improves efficiency in some situations, but Subaru's (i wouldn't recommend this for any other A/C systems) do great by simply fixing leaks and charging. 

Cheap, No tools, no vacuum, high success rate, nearly zero risk - it's a great fit for many people. 

[Theophilus]

They have no way of knowing if you need 10 ml or 100 ml, of PAG, that's why they don't include any. 

 

But that's just it - they DO know how much I'll need!

 

The oil that is added with a new receiver drier is meant to replace the oil that went out in the old receiver drier.  So anyone buying this particular new part will be replacing the same old part and will ALWAYS need to add exactly 10 mL (1/3 oz) of PAG oil.  There's no guesswork about it at all. 

 

(One-third of an ounce, by the way, is exactly what you get in a Heinz ketchup packet.  Imagine if the burger joint didn't include that with your order and just told you to go to the store for an 8 oz bottle of ketchup every time you bought a side of fries.)

 

Anyway, rant over.  Thanks for all the input in this topic!  I think I've decided to skip the 10 mL of PAG oil for now.  It's such a trivial amount that I can't imagine it makes much difference, and it wouldn't surprise me if the new receiver-drier actually had some oil already in it.  I'll let you know later this summer how it all turns out.

[carfreak85]

Theophilus, my point is, how sure are you that there is only 10 ml of PAG in your drier?  Your A/C system is designed to run a fixed volume of oil, let's call it 100 ml for the sake of argument.

 

You decide your drier is finished and remove it to put the new one it.  How much of the 100 ml of PAG your system needs is in that drier?  10 ml?  50 ml?  Unless you measure how much oil was captured in the drier, you will have no idea how much needs to be added.

 

Does that make sense?

 

Taken directly from my employer's HVAC service manual:

 

"Under normal operating conditions oil is circulated through the A/C system with the refrigerant.  When the system is not operating, the oil settles to the lowest points in the system.  These low points are typically the suction lines and the evaporator.  Oil will usually settle out in the cooler parts of the system.

 

When a component is serviced the small amount of oil that is retained in each of the components must be replaced.  It is necessary to balance the oil charge in the vehicle when servicing components and/or the refrigerant charge...  It is important for proper compressor lubrication that this amount [of oil] be maintained as close as possible to the design intent."

Edited June 21, 2016 by carfreak85