MACS Monthly Newsletter - 2017 - OCT6

a typo - there's no such word as hydroscopic), that
even re-closing the container isn't good enough to
keep moisture out of the oil. In fact, most of these
oil containers arrive in vacuum sealed packaging
that protects the oil from being contaminated with
moisture. See Figure 7.

are wrong, and he puts an entire 8-ounce bottle into
the system (not an unrealistic proposition), what
will happen? Will 11 ounces do any damage? Will it
completely fill up the compressor body? Or will it
spread out around the system? It would seem that,
over time and as the system operates and stabilizes,
all of the oil would eventually make its way to the
compressor body and stay there, since the oil separator will only allow a very small amount to leave.
So then will that excess oil cause problems? Will it
lock up the compressor, or maybe cause it to work
harder (since the internal workings of the compressor will now be operating in a pool of oil instead of
a thin mixture of refrigerant and oil)?

THE SIZE OF THE OIL BOTTLES

October 2017

Steve Schaeber

We've spoken with several of our MACS Member
service shops who are currently servicing the fleet
of yf vehicles, and we've noticed that since these oil
charge amounts are so small, the quantity of some
specific oils being sold by dealers is also very small.
We also received phone calls from members who
perform mobile A/C service and repair for body
shops, and one popular question was about the size
and contents of the factory oil can.
For example, the 2016 Honda Civic uses R-1234yf,
and its total oil charge is between 77 and 102ml
(2.7-3.6 ounces). When you buy the factory recommended oil (RL-85HM) from the dealer, you get an
8-ounce-sized metal bottle that's only filled with
40ml (1.35 ounces). The oil itself is not cheap, and
since it costs about $15/oz., they want to give you
something substantial that you can hold in your
hand (imagine the bottle size required for just 1.5
ounces). Not only that, the industry is quite used
to seeing and using these 8-ounce-sized bottles,
which are inexpensive and readily available, and
so changing doesn't make much sense. The larger
bottle size also helps make it easier to handle, pour
(and not lose) in the shop.
Most of your yf oils are not a typical PAG or POE,
but rather a special type that has been engineered
with different additives depending on the compressor that they're designed for. Some oils have anticorrosion, anti-oxidation or anti-wear properties,
while others contain additives such as acid reducers; it all depends on the compressor. That's why
it's so important to use the proper, recommended
oil as per the specific OEM that you're working
with.
There's another thing to consider, and that's the
shelf life of the product. Many times, when you
purchase these oils they have a warning on the
package that says something like, "Open the bottle
and use the product immediately. Throw away any
unused oil within 2 hours after opening." That's because the oil is so very hygroscopic (no, that's not

Figure 7: Many bottles of POE oil arrive in a sealed container, which is then
sealed in a plastic bag. The idea is to protect the oil as much as possible from
becoming contaminated with moisture.

THE 25% RULE
For a long time, we used a rule of thumb which
basically said that the oil charge amount is generally
around 25% of the total refrigerant charge amount.
For example, if you're working on a 2011 Kia Sedona (with a 3.5L V6), the specs say it takes 900±25cc
(about 31 ounces) of R-134a and 210±10cc (about
7.25 ounces) of FD46XG PAG oil. Do the math, and
you come up with about 23% (try this on a few more
vehicles, and you'll get similar results).
There are known exceptions to this rule, such as
the Jeep Cherokee (XJ). It uses 20 ounces of refrigerant and 8 ounces of oil, which works out to a ratio
of 40%. These FOT (fixed orifice tube) systems use
more oil per ounce of refrigerant than almost any
others that are out there.
When in doubt, and there's nowhere else to turn
for information (when there are simply no other
guidelines to go by), we generally use this 25% rule,
which says that whatever the refrigerant amount is,
25% of that amount is pretty close to the correct oil
amount for that system. This method usually works
well, although it's an educated, experienced guesstimate of what's right, and it's certainly adjusted on
a case by case basis.

MACS Service Reports

Table of Contents for the Digital Edition of MACS Monthly Newsletter - 2017