hello im new here and i was just wondering wether my gauge is bad or there is something wrong with my oil pressure. at cold start ups the gauge reads at about 100 (im assuning its 100 the line between 60 and 120 on the stock fd gauge) and quickly drops down to below 60. then when fully warm the gauge reads at about 15 and at about 3k rpms it up to 100. help please?

thanks in advance

 

The oil pressure will rise and fall based on rpm and temperature of the oil. i.e. cold oil and the 3000 rpm kick by the Accelerated Warm-up System will peg the oil pressure gauge. Oil thickness also plays a roll into the reading (i.e. higher pressure for heavier oils). Here's Mazda's FSM section on oil pressure:

 

that line would be 90(60+120=180/2=90). it's really easy to figure out how a gauge is graduated. cold oil is thick and will have a higher pressure reading. as it heats up it gets thinner causing a lower pressure reading.

 

i know about the oil pressure changing with temperture but its just seems funny becuase within the first 30 seconds the oil pressure drops a good 30 psi but i might just be paranoid about my car

 

i kind of have the same thing going on. i started my car, oil pressure is at about 60psi warmed it up drove around a little parked at a friends house. left my friends house and just as i was about to pull into my driveway i notice that my oil pressure is at what seems to be 100psi (its was a little below the line that says 110psi) i was wondering if this was my gauge being out of whack or if this was the natual temp of the oil once it had been warmed up.