I refilled an R22 window AC with R134a and this is what happened

[coolguy4]

I did this purely as an experiment, NOT because I thought it would work and I definitely do NOT suggest that anyone try this with a system that they care about. I got a free 8000 BTU Kennmore window AC from the 1990s that I use as a dehumidifier. Over the winter, it developed a slow leak and was empty yesterday when I turned it on and did not cool at all. I installed a Bullet Piercing Valve and filled it with compressed air to find the leak. The condenser had a pinhole, which I soldered closed and vacuumed the system to remove any air or moisture. I turned it on, connected the gauges and started adding R134a refrigerant. It took about 12 ounces of the original 13.6 ounces until it was cooling well and was not developing frost on the evaporator. The performance of the system is identical to with R22 refrigerant. It blows 38 degree air with a room temp of 75 degrees with the fan on high speed. I thought that the air would be warmer because I thought that R22 was better than R134a in terms of efficiency. But what I thought was the most interesting is how much cooler the compressor runs. With R22, the compressor and discharge tube got so hot it would hurt to touch. With R134a, the compressor runs MUCH cooler. It is still hot, but I can hold my hand on it for at least 5 seconds without getting burned. Same with the discharge tube. I have no way of testing it, but I would think that power usage would also be lower. Besides the obvious oil issue, what is the disadvantage to running the system this way? The pressures are MUCH lower, the system runs cooler and even seems quieter and it seems like it vibrates much less, but that makes no sense to me. I have no idea about longevity as I just started using R134a in this system, but it seems like it works great. What are your thoughts?