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Measuring Proper Oil

mattd860 on Fri April 23, 2010 12:47 PM User is offline

I need to measure and add approx 6.75oz of mineral oil to my system. Do I measure this liquid oz the same way I do refrigerant - by weighing 6.75oz on my digital scale? I ask because when I weigh 6.75oz, it just seems like way too much. Sorry for the noob question

HECAT on Fri April 23, 2010 1:20 PM User is offline

liquid ounces are volume, not weight.


HECAT: You support the Forum when you consider for your a/c parts.


GM Tech on Fri April 23, 2010 1:29 PM User is offline

True- liquid is measured in Fluid Ounces--- but the relationship of refrigerant oil weight to fluid ounces is very close-- I experimentally determined it years ago as a ratio of 1.1 to 1-- but I forget which way it is-- so if you already "measured" in the oil by weight, then you are not far off-- certainally not enough to mean any problems. You can do this also by simply weighing your measured volume.

I used to weigh new accumulators against the old ones, to determine how much ol remained in them, soaked up in the desiccant bag.

The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

mattd860 on Fri April 23, 2010 2:38 PM User is offline

Ok - so i guess i'll just use one of my wifes cooking measuring cups and measure 6.75oz

NickD on Fri April 23, 2010 3:29 PM User is offline

1 fluid ounce = 2 US tablespoons
8 fluid ounces = 1 US cup

Just use a baking type of measuring cup, a tad under 7 ounces.

If you have a beaker calibrated in cc, have to do some math, a fluid ounce is equal to 29.5735297 cc so you need 6.75 times 29.5735297 or or close enough to 200 cc or 200 ml.

One gram of water is equal to 1 milliliter, that can be converted to ounces. A weight to volume conversion. In terms of fluid ounces, oil weights a bit less than water, since oil is less dense than water, for an equivalent weight, will have more volume in fluid ounces, or same volume, less weight.

Typical domestic systems use a cup of oil, seems like a lot, but gets dispersed all over the place.

Screwed up on my decimal point, above is correct from converting from English to metric. 1 cubic centimeter is the same as 1 milliliter.

Edited: Fri April 23, 2010 at 5:17 PM by NickD

mk378 on Fri April 23, 2010 3:52 PM User is offline

PAG oil is probably denser than water. Pure polyethylene glycol is.

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