Mineral oil/R12 Ratio variance

[FStanley]

While researching the amount of mineral oil to R12 Freon for my 1978 Olds Cutlass, it takes 8 oz of mineral oil to 60 oz of R12. Ratio 13.3%

as you know other 1978-87 G Body vehicles are similar like Chevy MOnte Carlo, El Camino Buick Regals, Pontiac Grand Priz etc etc

I looked at the capacity chart from Four Seasons here:

https://www.4s.com/media/5421/four-seasons-capacity-guide.pdf

I compared some other ratios 1878-87 G Body cars from this chart. It was quite a range. Yes I know most say in the chart to look at the hood decal..

For example I noticed a 1987 Buick Regal was 8 oz Mineral oil to 52 oz R12 Freon Ratio 15.3%

1985 Pontiac Grand Prix was 8 oz Mineral Oil to 36 Oz R12 Freon Ratio 22.2%

when I look up that AC parts for 1978-87 G Body vehicles most are the same,

SO not understanding the wide variantion of ratios in different vehicles(they are all G Bodies), I would expect the ratio to all be the same for these.

Any idea of why?

 

[gnvair]

I used the GM service manual for my cars. They list the exact amount of oil for each component.

 

[69hurstolds]

Again, don't just add up the components. From what I've seen, you use the "each component" oil amounts if you're doing a partial piece replacement. Every CSM I've seen for G-body R-4 systems has partial amounts when they lead off with something like "system uses 6 ounces of 525 viscosity oil...blah blah" and then goes into telling you about component replacement and oil amounts. Yeesh. If you just add up the component replacement amounts, you'll likely add too much oil. It is customary to add an extra ounce or 2 of oil to a new accumulator as the dessicant will absorb some oil you'll never get out of it again. This MIGHT be where they're getting that 8 ounce crap on the 4 seaons chart. But R-4 systems on 78-88 Cutlass uses 6 ounces of mineral oil with R-12.

That chart has holes in it. They're clueless. 86-87 Cutlass shows 48 oz. of R-12 on the chart. Bullcrap. It's 52 ounces (3.25 lbs) per the decal on the HVAC box. Not even sure if they have the 88 as a FWD or the Classic RWD. The 88 Classic is also 52 oz. (3.25 lbs)

80-84 Cutlass. 3.25 lbs.

85 Cutlass decal. 3.25 lbs.

Here's an 86 decal, BOP. 3.25 lbs.

87 442 here. Oh, 3.25 lbs. It's correct for an 86 and 88 as well. Same decal.

NOS 84-early 86 Cutlass Compressor. Same size and oil requirements as any other R4. 6.0 ounces of mineral oil for R-12 system.

NOS 87-88 Cutlass 622 Compressor. Another 6.0 ounces. The amount is for a complete system.

I also was poking around the internets looking at low mile original 78 Cutlass with R-4 compressors. Best I can tell, they came with a 1131129 compressor.

However, the one halfway decent decal shown which was at an angle that was tough to read other than the upside down 129 on it, was on a 78 with a 17K mile 260 V8 in it.
It looked more like this.

Here's where it gets good. This is stuff STRAIGHT OUT OF THE 1978 CSM....

Cutlass V6 station wagon and V8 Salon use an R4 compressor. All other Cutlass is supposed to have an A-6.



And...from page 1B1-2:

So we know now that it is, indeed, 60 oz. of refrigerant on all 78 systems except Starfire and Omega. It is also 1/2 pound more than 80-up Cutlass.


Now, here's the oil distribution. Read the 1st paragraph carefully and stop. Let that sink in. It says the SYSTEM. Not to mean just the compressor. Now, read the 2nd paragraph where it says adding oil to the system when repairs are necessary. It's not really cumulative. If you just replaced the evaporator, you would add 3 ounces of oil into the evaporator and button it back up, draw down the system and put in the refrigerant. Because there are 2 different possible types of compressors used depending on the model and engine, it can get confusing the way this thing reads.

Electrical schematics always are a help, just in case, as well. You know, in the event you need to figure out some wiring. Hopefully not.

 

[69hurstolds]

Oh, and here's a picture of a 1985 Grand Prix. 3.25 lbs of R-12 refrigerant needed. Gotta look close. But it's there. No different than the 85 Cutlass label above.

 

[78Delta88]

Plus there are the lines. Compressor on driver side HVAC box on passenger side compared to AC Compressor on the passenger side. Big difference between 1.5 foot 1/2 inch diameter return or a 2.5 foot 1/2 inch return line. Same for supply lines even though typically smaller diameter.

 

[69hurstolds]

Plus there are the lines. Compressor on driver side HVAC box on passenger side compared to AC Compressor on the passenger side. Big difference between 1.5 foot 1/2 inch diameter return or a 2.5 foot 1/2 inch return line. Same for supply lines even though typically smaller diameter.

Makes perfect, logical sense, but I guess they were lazy with labelling? 1978 had 260 or 305. Radial compressor on the passenger for the 260 and on the driver side for the 305. Same oil and refrigerant requirements. It does not differentiate in any of my CSMs.

In fact, that 86 HVAC label above is on a Monte SS. Same decal as an 86 442. So the question is, maybe the 3.25 and 6 oz of oil are good specs for the Chevy, and they just didn't change requirements for the shorter-hosed Olds? Who knows. And it really isn't an excact science anyway.

I'm sure an ounce or two extra isn't going to kill anything. Accumulator will hold some of it. It's just that if you start getting TOO much oil everywhere, it could start messing with heat transfers and all that mess, not to mention a potential for hydrolocking your compressor which would be bad. No need for 10 or 12 ounces of oil in an R-4 system, for example.

 

[gnvair]

I have found the GM service manuals are very good IF you can't pour out each component and measure the amount of oil that comes out. I am speaking from my own personal experience. A charging station would be ideal if you know the amount of oil the system requires. But without a charging station the manual works best. My latest set up I did this with is the custom serpentine set up on my Malibu that I charged with R12. For that I used the capacities from 1988 Monte Carlo service manual as I figured they were the updated numbers over the 78 manual.

 

[69hurstolds]

True, the GM manuals are pretty good when you need the correct information specific to your car providing you're using factory style equipment. But when you do custom setups and such, parameters may change so it's up to you to make adjustments accordingly. For example, if you use 134a you'll obviously use less refrigerant. Or my 152a experiment I'll only need like 30 ounces vs 52 for R-12. Plus, the service manuals can't predict the future. R-12? Not practical any more. The only flushing refrigerant GM acknowledged back then was R-11. Can't do that anymore either. Again, adjustments need to be made.

But unless you've owned the car since new, you may not know what is in the system. And in those cases, especially conversions, I will do a flushing of the system and replacing as many components as possible with new, especially the accumulator, hoses, and/or condenser. YMMV.

 

[gnvair]

True, the GM manuals are pretty good when you need the correct information specific to your car providing you're using factory style equipment. But when you do custom setups and such, parameters may change so it's up to you to make adjustments accordingly. For example, if you use 134a you'll obviously use less refrigerant. Or my 152a experiment I'll only need like 30 ounces vs 52 for R-12. Plus, the service manuals can't predict the future. R-12? Not practical any more. The only flushing refrigerant GM acknowledged back then was R-11. Can't do that anymore either. Again, adjustments need to be made.

But unless you've owned the car since new, you may not know what is in the system. And in those cases, especially conversions, I will do a flushing of the system and replacing as many components as possible with new, especially the accumulator, hoses, and/or condenser. YMMV.

On mine...I started with fresh and dry components. The compressor was a new Delco unit that I emptied and added the amount of mineral oil in the service manual. Adding the amounts of mineral oil to directly to each component worked out very well for me as it has many times in the past. You can throw all of this information out when you bring 134a or different refrigerants and oils into the equation. But from my experience (35 years working in the automotive field) you cant go wrong using the GM capacities if you are dealing with an R12 system and using factory sized components.

 

[FStanley]

Bottom line you can't trust the Four Seasons Chart.. refer to service manual for year and car and also look at existing AC lables..