For what it's worth, I'll throw this info in here. I say this because I've mentioned this product on other forums and got nothing but haters and flaming. But this does not seem to be that sort of forum and so.... here goes.
I've been using Maxi-Frig for going on ten years now. This is because almost all of my vehicles had the old R22 stuff. I got really sick and tired of all these guys who came forward representing themselves as know-it-all experts and giving me a million reasons why a certain this or that could not be done... *SNIP* ... Instead of using R22, I put in the Maxi-frig and it's been the best working Volvo AC we've ever had in this family.
Later, I did the same thing with my mom's 1992 GMC mobility van. It had a dual system with an accumulator/orifice tube in the front system and an exansion valve in the rear system. Charged it with Maxi-Frig again and again... excellent results.
At the risk of sounding like one of your know-it-all experts (not flaming or hating, just speaking my experience), as I said earlier, I have never seen an automotive system (prior to R134a) that used R-22, only R-12. While your dealer-installed Volvo systems may well have been R-22 for all I know (I've never seen a Volvo system, and dealer-installed options are almost never the same / as good as a factory option, usually non-standard), I can't think of any reason they would have been.
There is a reason that different types of refrigerants exist. This is because different types of systems, have different operating parameters, different capacities, and different operation pressures and conditions, thereby requiring different refrigerants suited to each system's characteristics.
Using the wrong refrigerant in any system can and will destroy it, if it even allows it to run at all, not because the system knows what refrigerant is in it, but because the control system is set for the operating parameters of the refrigerant it was designed for, and it simply will not operate properly any other way. The one exception I know of to this rule is the rather common retrofit of R-12 systems to run on R-134a.
FYI, factory R-134a systems are generally disproportionately sized in comparison to R-12 systems, and R-134a refrigerant has a slightly different molecular structure, so while a retrofitted R-12 system will work just fine, it may not perform quite as well as a factory R-134a system or as well as the R-12 system's original R-12 did.
As an example, here is a link to refrigerant system charge capacities for various Oldsmobile models, some years using R-12, some using R-134a. You can see for yourself that the R-12 systems generally take more refrigerant, especially the older ones, as it is a bigger system. This seems to vary with R-12 systems that used PAG oil as opposed to the traditional mineral oil.
Oldsmobile A/C System Refrigerant Capacities - R-12 and R-134a
A good example is the variance from the 1993 Bravada to the 1994 Bravada, without rear A/C. Otherwise, the same vehicle. Also, the Ciera's varying years show a different charge capacity when factory systems began using R-134a. Also, being based on GM's FWD A-body, they were otherwise the same vehicle from 1982-1996. I know, having owned several.
For the application in this post, here is a link to the refrigerant capacities for the systems used in Ford light trucks dating back to the mid/late-80s. Scrolling down, you can find the E-350, which clearly shows the systems got smaller when R-134a was introduced. Ford's E-series van was practically identical and unchanged otherwise from 1992 apart from engine options and minor styling changes until official production was ceased in 2015, though it is rumored to still be available as a cutaway commercial cab/chassis.
Ford Light Truck A/C System Refrigerant Capacities - R-12 and R-134a
Moving along, R-22 is a higher-pressure refrigerant that could easily blow out every seam in an R-12 system. This is primarily because it is designed for much higher-capacity systems. R-22 typically runs 50-65% higher pressure on the high side, one of several reasons no professional would ever put R-22 in a system designed for R-12. The R-12 compressors simply aren't designed to deal with that much pressure. I can also see where an overloaded compressor would put more drag on the engine, resulting in reduced fuel economy.
R-22 in an R-12 system would likely even destroy the compressor from such overload, eventually, if it ran at all. The cut-out switches would likely not even allow the system to run at all without being bypassed or replaced with switches set for higher pressure ranges.
It's sort of like running motor oil intended for a gas engine in a diesel (as many an Oldsmodiesel owner learned the hard way in the 1980s), or non-automotive spec motor oil in an automotive engine. It may do in a pinch, but if it runs very long at all, it will certainly have some detrimental long-term effects.
As to this Maxi-Frig product you speak of... I've not heard of it until now, so I can't say for sure whether it is snake oil or not. Your post indicates that it may be a multi-purpose refrigerant, though it would certainly be the first I had heard of one. Don't take it as hating or flaming, I'm merely skeptical of something I haven't heard of. One red flag for me is that you say you charged a GM van again and again with this stuff, indicating that it was higher pressure than the system called for, which would have exacerbated any existing leak.
(UPDATE) However, on checking the site, Maxi-Frig indicates it is merely a brand name that indeed comes in different system types and specs (R-22, R-134a and R-12 are all clearly listed on the website you linked to). Seems to me this is a super-refrigerant that indeed works better than the standard type unique to a particular system, but its merits may well require a perfectly healthy system with no issues, and may cause small problems to become big ones. At the end of the day, it still has to be the proper type (R-12, R-134a, etc.)
Most chain auto parts stores, even Mal-Warts, sell 'hot-rod' synthetic 'booster' refrigerant, as it were, for R-134a systems, most of which I've seen under labels such as Arctic Chill, Super-Cool, Arctic Blast. Perhaps Maxi-Frig is simply another label for such a booster, and most I've seen do exactly as they claim. I've used Arctic Freeze and SubZero from Auto Zone to boost a few R-134a systems myself. (END UPDATE)
Though I do speak from limited experience, I learned mostly from my father, who was an industrial/commercial HVAC control contractor for years, and also knows the nuts and bolts of these systems. I have seen and helped him charge many a residential system with R-22 over the years, as well as many automotive systems, some restoring an R-12 charge, some converting to R-134a, NEVER R-22.
Side note: He happens to have a 1992 GM conversion van that has the rare distinction of still holding its factory charge of R-12. No offense or disrespect intended, but I think you may be confusing R-22 with R-12.
Again, not being a know-it-all, just explaining why I know what I know.
