View Full Version : 93 SD709 compressor - PAG or Mineral oil?

July 5th, 2006, 09:09
I am doing a 4.0 swap and putting a 93 4.0 in a car that already has R134 air.

Does anyone know if the 93 SD709 compressor came filled with PAG or Mineral oil? It was an R12 system, but I believe some manufacturers began using PAG oil in the mid eighties.

I have AC tools and know how to work on it, but I have never run into this question before! If the compressor had mineral oil in it, can I drain as much as I can out and put PAG in, or must I put something like Ester oil in it (something compatible with both freon).

On a side note... is there a benefit to switching to the newer 134 ready SD7H15 compressor?


Rick Anderson
July 5th, 2006, 09:20
From what I understand;

Mineral Oil will not work with R-134a, its non-miscuable, basically it won't mix and move with it thru the system and thus not lubricate the system.

PAG Oil can NOT be used with R-12, the chlorine in R-12 will contaminate it and destroy it. I do NOT think any manufacturers were using PAG oil with R-12, I'm almost sure that it will NOT work, someone correct me if I'm wrong.

PAG Oil is miscuable with R-134a and is what is used with it.

POE or Ester Oil is miscualbe with R-134a, its not as good as PAO Oil, but its more tolerant of a little bit of R-12 and/or mineral oil than PAO is, thats why its used for conversions, in case there is a little bit of R-12 or Mineral oil left over.

If you know for a fact the compressor was used for a R-134a system, then it must have used PAG Oil and thus you can use PAG Oil.

If it was R-12 or you don't know, use Ester/POE Oil, it will be more tolerant of any residual mineral oil/R-12 that remains in the compressor.

Try to drain as much oil as possible from the compressor, you don't want mineral oil in with the PAG or POE oil, and even if it was PAG/POE in the compressor to begin with, those oils are hydroscopic, meaning they absorb moisture out of the air that degrades them. So any PAG/POE oil that has been sitting in an open compressor that has been sitting around is most likely bad.

July 5th, 2006, 12:00
Thanks. The systems I have worked on before have had new compressors. I think I will drain the compressor as good as I can and put estercool in it.

July 5th, 2006, 16:55
Don't know about the oil, but we had the same compressor (new) put in son's 88 XJ when we converted to R134a and it has been working real well.

July 5th, 2006, 17:08
You could always upgrade to R-406a, it is a R-12 alt... uses the same setup...included the mineral oil, but needs the newer Barrier hoses... And No I don't mean R-414B (hotShot)... R-406A is colder then R-12, but not bad for the Ozone... well as much and it legal to use in Cars, Truck, SUV's...

July 5th, 2006, 17:33
AutofrostTM(R-604a) / Autofrost X4TM R-12 Replacement Q & A’s
Q. What is Autofrost refrigerant?
A. Autofrost is a blend of refrigerants R-22, R- 142b, and a small amount (4%) of R-600a, that is a substitute refrigerant for R-12 in
stationary and automotive A/C systems. The 4% R-600a aids in returning the mineral oil to the compressor and is such a small amount,
that Autofrost stays non-flammable. Even after worst case leaking and recharging Autofrost still has no “flash point” and will not sustain
a flame. No oil change is needed. Autofrost was invented by George H. Goble (GHG) and is marketed by Monroe Air Tech
Q. What is Autofrost X4 and how is it different from Autofrost?
A. Autofrost X4 is very similar to Autofrost. It consists of R-22, R- 142b, R-124 and a small amount of R-600a (to provide a good mineral
oil return). Autofrost X4 is basically Autofrost with a small amount of R- 124 added and is also non-flammable. Suction pressures are the
same as Autofrost and the head pressure will be slightly higher, about 5 PSI higher at 130 degrees F condensing temperature. This blend
also carries a UL listing ( Underwriters Laboratories ).
Q. Are these products legal to use?
A. Yes. Autofrost and Autofrost X4 have been found “acceptable” by the E. P. A. and was printed in the Federal Register on October 16,
Q. Does this refrigerant have to be charged as a liquid?
A. Yes. This refrigerant and all other zeotropic blends (R-400
Autofrost/Autofrost X4 are supplied in 25 lb. cylinders which
inverting the cylinder.
Q. Should I always vacuum the system before charging?
series) must be charged as a liquid to prevent change in composition.
contain a “pickup tube” to withdraw the product as a liquid without
A. Air and moisture will not condense and will cause excessive high side pressures! This
especially the hoses. Always pull a vacuum at 29.9 inches of mercury for at least 30 minutes before
Q. How much Autofrost/Autofrost X4 do I need to charge in?
can cause damage to the system,
charging, 45 min. to 1hr is better.
A. If you are using scales to weigh it, then use 80% of the R-12 weight amount. If you are using a liquid charging cylinder such as
DIAL-A-CHARGETM, use the same liquid amount as you would R-12. Some systems will perform better with less than the recommended
Q. Why do I use only 80%?
A. Autofrost is lighter in weight than R-12 (like antifreeze and water). The 25 lb cylinder of Autofrost is the same size as 30 lb of R- 12.
The Autofrost 9.6 oz can is the same as the 12 oz can of R-12. When comparing prices, always divide by 30 lbs.
Q. What is the best procedure for charging?
A. Before starting engine, charge up to 60% ( 2.5 lbs R-12 X .60 = 1.5 lbs Autofrost ) of determined amount through the low or high side
port as a liquid only. DO NOT TURN CYLINDER UPSIDE DOWN! ( Cyl. has a pickup tube and must remain “valve up” ). Allow the
system to stabilize for 3 minutes, then start engine. Turn A/C on Max., wait 3 more minutes and then add up to 20’% ( 2.5 lbs R-12 X .20
= .5 lbs ) more Autofrost through low side port only. Performance may be acceptable at less than 80%. Total maximum charge is 80%(
2.5 lbs R-12X .80 = 2.0 lbs Autofrost )
Q. How should the system perform?
A. If you did a performance check on the same system with R- 12 and Autofrost, you would see a 3 to 5 degree improvement with
Autofrost No two systems will perform exactly the same, but the readings will be very close on the suction side. High side pressures will
be within 15% of R-12 pressures depending on condenser design, airflow and ambient temperature. If you experience excessive head
pressure, check for a dirty radiator. Small debris can get through condenser fins, get caught in the smaller fins of the radiator, and is
undetectable without removing top covers and visually inspecting. Dirty radiators, inside and out will cause heat to soak into the
condenser and cause excessive pressure in the system even after the vehicle is parked! It is wise to always measure refrigerant charge.
Something as simple as a digital bathroom scale will be closer than guessing. Remember too much can do damage!
Q. Can I use automatic charging equipment with Autofrost?
A. It depends. Older type automatic charging equipment, which uses a FLOW METER to meter in R-12 at a fixed rate should be checked
with a scale. For example, pull a vacuum on an empty recovery tank and place it on a scale. Program 3 lbs on your charging station and
note the weight added to the empty tank when the machine stops charging. The number scale on your machine can be altered to the
correct amount. Newer type equipment, which contains a set of scales to weigh in a measured charge (remember to only use 80% as much
Autofrost as you would R-12) to a holding tank before charging should work all right. Remember to use the same liquid (level or
volume) here as you would for R-12.
Also, most R-12 automatic charging equipment withdraws the product (R-12) from a 30 lb. cylinder as a liquid, and the R-12 cylinder
must be mounted upside down when attached to charging equipment. Autofrost 25 lb. refrigerant cylinders contain a “pickup-tube”.
Much like a can of spray paint, such that you get liquid out when the can is upright. Autofrost cylinders MUST BE INSTALLED
UPRIGHT when used in charging equipment that is designed to have R-12 cylinders installed upside down. You may have to lengthen or
splice in a small piece of hose if needed. Also, use only automatic charging equipment that withdraws the product from the refrigerant
supply as a liquid.
Q. What about the old “feel the evaporator outlet line” and charge “until it gets cold” method of charging?
A. Blends such as Autofrost sometimes need two or three minutes (at idle speed) to become thoroughly mixed throughout the system.
Often, when the evaporator outlet line begins to get cold, the system will be overcharged. Solution: as you near the end of charging. stop
charging for 2 or 3 minutes and let the system continue to run at idle before performing further charging or diagnosis. If a large part of
the initial charge is dumped into a suction (low side) accumulator, such as on a typical GM CCOT system, the higher boiling components
of the blend will hang around in the accumulator longer than R-12 would. Please take an extra 2 to 3 minutes to let the blend mix
completely before proceeding.
Q. Does this refrigerant need to be recovered (captured) ?
A. Yes. Under US EPA rules and regulations, all CFC, HCFC, HFC refrigerants and just about anything else needs to be recovered and
not be vented into the atmosphere. Refrigerants which require recovery are R-12, R-22, R-134a, Autofrost, and all the other current
“legal” R-12 replacements at the current time. The only refrigerants which may be vented are air (nitrogen), water, CO2, ammonia, and
pure hydrocarbons according to US EPA rules. You are not likely to encounter any of these, as they will not work and will damage the
Q. What are EPA retrofit fittings?
A. The US EPA is requiring special “uniquely threaded” fittings to be attached to all R-12 service ports. These fittings provide threads
which are unique to each type of alternative refrigerant. These fittings are required by law (only for the automotive sector, does not apply
to stationary equipment) for refrigerants which have completed the entire EPA approval process and are listed as “acceptable” for mobile
A/C. Refrigerants MUST be properly labeled some where under the hood. These labels are packaged with Autofrost. All other refrigerant
labels must be removed or rendered unreadable. Retrofit fittings for Autofrost are available from suppliers of Autofrost and cost around
$5 each. Adapters to hook up R-12 equipment are also available.
Q. What about “topping off" systems low on charge?
A. Current EPA rules only permit “topping off’ with the same type of refrigerant which is already installed in an automotive system. For
systems charged with zeotropic refrigerants such as Autofrost, or almost all other “blends”, the recommended procedure is to first remove
(recover) the charge and recharge with fresh virgin material. As zeotropic blends vapor leak, they change composition (pressures get
lower), and a recharge will result in lower pressures, and some reduced capacity. However, many technicians have topped off Autofrost
systems and report no problems. The property which makes Autofrost change composition (called fractionation) as it vapor leaks, is also
responsible for a big performance gain over single component refrigerants such as R-12 or R-134a. Zeotropic refrigerants exhibit a
temperature “glide” (about 16 degrees F for Autofrost), which causes the refrigerant to boil (evaporate) or condense over a range of
temperatures instead of a single temperature, thus increasing the heat rejecting capacity of the condenser and increasing cooling
performance over R-12 and R-134a.
Q. How will refrigerant identifiers read Autofrost?
A. All refrigerant identifiers currently available are designed to read R12 and 134a. If virgin Autofrost is entered, it will show Rl2, 134a,
and hydrocarbons. Keep in mind that oil used in the system will also show as a hydrocarbon. Some major equipment companies have
purchased Autofrost and are working on a new identifiers that will give true readings on all GHG products.
Q. Are compressor seal kits and system o-rings compatible with Autofrost?
A. Autofrost works best with neoprene. GM uses neoprene seal kits and o-rings and are available from A C Delco distributors, Neoprene
seal kits for other compressors such as Ford, Chry. etc are available from EMC Inc. at 800-621-8774. Monroe Air Tech Inc. will also
have these kits available soon. When R-134a was developed, a new o-ring was also developed known as HNBR. The HNBR seals are
generally green in color and have been introduced to the automotive industry as being superior to all other rubbers. However it is now
known that the HNBR seals are only compatible with R-134a. It is recommended that you ask for neoprene since it is compatible with all
refrigerants including R-134a
Q. Do the hoses, driers, or the oil need changing?
A. In general, no. Most American built cars have used nylon lined “barrier” hoses for years. These are fine for Autofrost Some real old
cars, foreign cars, and cars with “port of entry” add - on A/C systems may have “nitrile” rubber hoses, which can leak R-134a and all
currently legal alternative refrigerants at a higher rate, It is therefore recommended that nitrile rubber hoses be replaced. All current
replacement hoses are now of the barrier type. Unless the oil is contaminated by a system failure, it does not need to be changed,
Autofrost works fine with the standard mineral oils (usually 525 viscosity) used in R-12 systems and does not require any additives. If
you change the oil, replace it with the same mineral oil as was in the R-12 system. Alkylbenzyne based (AB) oils also work fine.
Q. Compressor suppliers (automakers) are sometimes shipping compressors precharged with PAG oil, what do I do?
A. Do not put Autofrost into one of those or it will probably fail. Local technicians have had good luck by ordering compressors “dry”
(no oil), and then charging mineral oil (on the bench, while turning by hand). Another alternative which local technicians have tried is to
take the PAG oiled compressor and purge it with mineral oil on the bench while turning it over 30 or 40 times by hand to work almost all
of the PAG oil out. Both dry and formerly PAG - charged compressors have been in the local area for over two years in service with
R-12 and mineral oil.
Q. What do I do with used refrigerant?
A. The best approach is to “recover” (capture it) into a standard gray and yellow refrigerant recovery cylinder and send it to a reclaimer to
be reclaimed to new refrigerant purity and composition. Some technicians may wish to “recycle” (clean it locally). If this is done, one
must make a “pressure-temperature” check to insure the composition hasn’t changed too much from leaking. Let a cylinder stabilize
overnight to some known temperature, say, 70 degrees F. Connect up a gauge and measure the pressure. Look up the correct pressure on
the Autofrost pressure-temperature chart. If the pressure is within 2 or 3 PSI of the listed pressure, you should be all right. If the pressure
is low, then the composition has changed from vapor leaking. The easiest thing to do with changed - composition refrigerant is to return
it for reclaiming.
By far the SAFEST and least likely to cause problems method for dealing with USED refrigerant (from cars which come to your shop), is
to RECOVER it into a cylinder and ship it to a reclaimer. You have no idea what is in the system without using expensive and not always
accurate refrigerant identification equipment. The owner or other shops may have charged in a pound or two of R- 134a, R-22, propane,
illegal blends (often propane/isobutane/butane blends), smuggled - in refrigerant of questionable purity, or other legal blends and not
properly labeled the system.
After doing an evacuation of the system, charge with only virgin (new) refrigerant or good refrigerant of known quality. If you have to
then remove the charge to do more work on the system, you may then want to “recycle” and reuse this charge you just put in, provided
there was no excessive loss of it due to vapor leaking,
Another legal, lower cost alternative to the high price of refrigerant recovery cylinders, is to use NEW BBQ grill propane tanks. These
are DOT rated at 240 PSI and are legal for shipping R-12 and similar pressure alternatives. A 20 lb. BBQ grill propane tank typicall y may
be purchased for about $15 at places such as Sam’s Club or other wholesale buyers clubs. Be sure you only use NEW tanks. If propane
was ever in the tank, it will “stink” for eternity from the mercaptain odorant. The reclaimer will get extremely mad at you and you will
have to pay upwards of $10/lb. to have the refrigerant burned if you do not use a new tank. Adapters are available from Autofrost
suppliers for adapting R-12 hoses to these tanks. The 20 lb. propane tank will hold 37 lbs. of Autofrost (the 80% fill level). Larger, 100
lb. propane tanks may be purchased new for around $80, and the hold 185 Ibs. of refrigerant. If you do use propane tanks, be sure to
contact your reclaimer first to make sure it is all right. Contact your reclaimer or refrigerant supplier for proper shipping instructions on
used refrigerant. A $10 or so “hazmat” fee (all compressed gases are shipped as hazardous) will usually be charged in addition to the
normal shipping charges. The tank will have to be properly marked for shipment and need “diamond” stickers, and other labels. For a $15
tank, you can tell the reclaimer to just “keep it” or sell it or throw it away, since it is cheaper to buy a new tank than to ship the old one

Autofrost Material Safety Data Sheet
GHG Refrigerant-12 Substitute(R-406A)
Chemical Family:
Halogenated Hydrocarbons+ Paraffinic Hydrocarbons
Mixture of C4H10 / CH3CClF2 / CHC1F2
Methyl propane /R- 142b or Isotron-142b or
or HCFC- 142b / R-22 or Freon-22 or Genetron-22 or
HCFC-22 /
R-600a / R-406A/ GHG R-406A
CAS Name: CAS Registry No.
Isobutane 75-28-5
1 -Chloro- 1, 1 -difluoroethane 75-68-3
Peoples Welding Supply
426 Brown St. Levee
W. Lafayette, IN 47906
Emergency Phone (24hr):
800-535-5053 or
Boiling (bubble) point: -26.23 F
Percent volatile by volume: 100
Boiling (dew) point: -10.05 F Mol. Wt: 89.97
Density (liquid 70 F) 70.27 LB/FT3 Pressure: 95
PSIA @ 70 F
Vapor density (Air = 1): @70 F 1.29 LB/FT3
Solubilty in H20: Slight
pH Information: Neutral
Freezing point: Not established
Appearance and odor: Colorless liquefied gas
faint ethereal odor.
Materials: Approximate weight % :
Isobutane (R-600a) 4
chlorodifluoroethane (R- 142b) 41
chlorodifluoromethane (R-22) 55
Stability :Material is stable. However, avoid open
flames and high temperatures
Incompatibility (materials to avoid): Strong oxidants.
including oxygen.
Freshly scraped aluminum, alkali metals, and alkali
earth metals (sodium, magnesium, etc.), may cause
exothermic reaction. Aluminum in refrigeration
systems contains an oxide coating, so it does not react.
Hazardous decomposition products: May decompose
at high temperatures (above 400 F-500 F), and from
contact with hot metal, heating elements, pilot lights,
internal combustion engines, and open flames.
Decomposition products may include hydrofluoric and
hydrochloric acids, chlorine, fluorine, possibly
phosgene, carbon dioxide, and carbon monoxide.
Polymerization: Will not occur.
Flash Point: None Chlorodifluoromethane: Low in toxicity at
concentrations as high as 4% (40,000 ppm). Narcotic
Auto Iignition Temperature: N/A effects have been seen at 200,000 PPM. Heart
efficiency (animal studies) has been reported to be
Auto Decomposition Temperature: 400 F -500 F or reduced at concentrations of over 25,000 PPM.
First Aid:
Fire and Explosion: Cylinders may vent or rupture in Inhalation: Remove to fresh air, call a physician. If not
fire conditions, leading to decomposition. breathing, give artificial respiration. If breathing is
difficult, give oxygen. Do not give epinephrine or
Extinguishing Media: Water spray similar drugs.
Special Fire Fighting Instructions: Use self-contained Eyes: Flush immediately with water for at least 15
breathing apparatus. Use water spray to cool cylinders minutes. Call a physician.
to prevent bursting or venting under fire conditions.
Product may be flammable if mixed with large Skin: Flush with water, warm slowly (cool water) if
quantities of air at greater than atmospheric pressure. frostbite. Call a physician
Principle Health Hazards:
Inhalation: Vapor is heavier than air and can cause
suffocation by displacing oxygen available for
breathing. Contact with liquid may cause frostbite.
Breathing high concentrations of vapor may cause
light headedness,giddiness, shortness of breath,
and may lead to narcosis, cardiac
irregularities, unconscienceness or death. May cause
eye irritation.
Toxicity / Exposure Limits: OSHA and ACGIH
Not established, but recommend TWA 1000 PPM.
Spill or leak: Using a self-contained air supply and
frostbite protection, personnel should attempt to close
valves or repair the source of the leak, if it is safely
possible to do so. If a large quantity is released,
evacuate personnel, and allow to dissipate.
Proper shipping name: Compressed Gas, N.O.S,
DOT placard: Nonflammable gas
Do not heat above 125 F
Humans exposed to Isobutane, 500 PPM, 8 hours a Other Information: Date revised: 11/15/94
day, 5 days a week, for 4 weeks, showed no
cardiac,pulmonary or other functional abnormalities. Person responsible:
George H. Goble
Chlorodifluoroethane: Inhalation-Rat -4 HR LC50 - Peoples Welding Supply
128,000 PPM 426 Brown St. Levee
W. Lafayette, IN 47906
317-743-3839 or 317-463-2672

July 5th, 2006, 19:04
You could always upgrade to R-406a, it is a R-12 alt... uses the same setup...included the mineral oil, but needs the newer Barrier hoses... And No I don't mean R-414B (hotShot)... R-406A is colder then R-12, but not bad for the Ozone... well as much and it legal to use in Cars, Truck, SUV's...
If you upgrade to this, make sure it is OK with the compressor manufacturer! Certain products (other than R-12 or R-134a) may void your compressor warranty!

July 5th, 2006, 20:19
In order for a automotive compressor must meet the EPA MVAC 609 standard they have to be certified for specific types of refrigerant. And freely list them for all to see... For newer type of compressor you may have to order them dry in order to make sure you don't cross contaminate the oils. But for an order system your warranty already has expired... which is why I explained to use a refrigerant that uses the same setup as the older banned R-12 oil... And remember that when converting a r-12 system to a R134a retrofit system you need to clean out 98% of the mineral oil from the entire system... only a less then 2% mix will ensure your system to function properly... that's not just the barrier hoses but the drier, evaporator, and condenser... but with a R-12 system convert to a R-406a all you need to replace(maybe if you don't already have them) is to add newer barrier hoses.