A shunt is pretty dumb simple and low risk as far as reliability goes. Far better to do a shunt near the battery than route the big wires through the dash and back out like we all used to. I mean, factory BCMs now have shunts as part of the battery terminals…. Our 2018 f150 has one, as does the 2015 crv.
gauge selection for me depends on how you use the car. I can work with volts or amps. Both helpful, both inter-related. Trans temperature is nice, but if I were to do it again, I’d rather monitor the rear axle temperature. That’s more telling in my experience, because it has no additional cooling, while the transmission is actively cooled. Unless it’s a 41TE in a minivan, that gauge was flat out entertaining. Vac/boost, though it probably gets old after a while. I leave my truck on in acc mode for hours and run an inverter at times - I have an led volt readout for just that reason. I don’t race or run hard, so oil temp isn’t a thing for me. I do solidly suggest oil pressure, especially in a midlife car getting older. Good to have a feeling for its behavior. Dropping oil pressure often suggested to me when oil was aging and thinning out, old school OLM.
i remember 2 cars where I added my own tach.
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