I bought a "mechanic's" oil pressure gauge some time ago; with a set of brass adapters to allow you to put it into your current sending unit location. It's got about an 18" flexible hose on it.
I always use it for initial startups and breaking periods BEFORE I install any original/aftermarket/ gauges or idiot lights on my projects. (New or old, I have found that they are not always the most accurate....)
I ran it for about 150 miles on my last project (under hood) before hooking up aftermarket gauge. (Turned out to be almost exactly correct, whew!)
Also, while we're at it... I always compare temp gauge readings with an infrared/laser, hand held thermometer. This allows you to move it around and check temps all over the engine, radiator, thermostat housings, etc.
Got sick of inaccurate temp gauges! I hate when they erroneously tell you it's overheating and you are freaking out on a hot summer cruise!
