when I'm driving the oil pressure gauge stays in the middle but when at idle it drops to 30 or under.

new to rotors so is this normal or is there something that need fixing? please help your advice is much appreciated

 

Hard to say. Sometimes its normal and sometimes it isn't. My brand new engine stays at about 50-55 psi above idle and slightly under 30 psi idle. Granted this is with a stock gauge and is unreliable.

 

then whats safe oil pressure for our cars?

 

Oil pressure specs are in the FSM (links in the FAQ if you need them). Offhand, it's something like 60+ psi at 3k RPM, but a 20+ year old sender isn't going to give you the most accurate pressure reading anymore. A mechanical oil pressure gauge would be the way to confirm if you're worried about it.

 

so an after market oil pressure gauge might be the way to go but can I just replace the sending unit or aftermarket gauge all the way?

 

a mechanical gauge work great!

every time i push gas pedal, show me the right press

 

Yes, you could replace the sender with a new one. Mazdatrix has them for $65. http://www.mazdatrix.com/86-92Electrical-Engine.htm

But before doing that, you might try the simple test outlined in the FSM (page 15-30 of the S4 manual). If you ground the sender wire with resistors inline, the needle should go to specific pressure values.

30 psi: 196.7 ohms
60 psi: 141.2 ohms
110 psi: 102.6 ohms

You can see that with more resistance, the pressure reading drops. If the resistance range of the sender has changed with age, or there is a poor/dirty connection, the pressure value will change.

 

wow really helpful, I will try this out thank you