308 Oil psi Gauge

I have a 1980 308 GTSi and am wondering about the oil pressure sending unit and the pressure gauge. My car runs like a top, good power, doesn't use very much oil at all, but the oil pressure seems to show a bit off??? The gauge is a 0 - 85 - 175 lb version, and the warning light works, so I'm not really concerned that I have an engine problem but the gauge never goes above 85. It mostly runs about 65-75, but when the engine is at full temp and at idle it's hardly above the 0 mark. Is this gauge just way oversized (i.e. the range is to large that the pressure will always appear at the lower end) is my gauge bad, how about the sending unit??? Couple of questions for you pros. Thanks