Does your car have a belt driven fan? If so the fan is spinning much faster when moving. Plus you get the airflow over the condenser from the wind. Both of those lower its temp, which lowers the high side pressure.

I'll have to look at that reading in my Passat. It has twin electric fans so their speed isn't dependent on engine speed, and they're very powerful to cool the engine bay during a 1100*F DPF regen.

-J

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.