I use an electronic/digital gauge as stated in my original post. They are very accurate. The DIC usually reads within 1 psi of my gauge when checking cold tires so apparently it is fairly accurate as well.The maximum pressure for the Goodyear OEM tires is 51 psi, so you are not exceeding that. However, the DIC units on my Volt read about 1.5 psi lower than the gauge pressure, so you may be pushing it. If it were me, I'd probably reduce the DIC-indicated pressure to about 44 psi.
I read somewhere that filling the tires with pure nitrogen, as they do at Costco, reduces the pressure variation with temperature because water vapor, which has a larger expansion coefficient, is excluded.
2014 Volt Premium - Safety pkg 1 and 2, Navigation