Hi, i'm new to this forum. I own a 99 Eclipse GST auto. My car is pretty stock, with bolt on's like a turboback exhaust and an airfilter.
A few months ago i noticed the oil sign coming on when i was idling or in slow moving traffic. It would disappear when i started driving. My car has a rebuilt head, stock bottom end with 158 k miles on it and a factory turbo with about 10 k miles on it. So my friend ( a mechanic) suggested i use non synth thick oil in it, and he added some 15w-40. When i saw the oil sign coming on, i thought it was because it was non synthetic and as far as i know, this car needs synthetic. So i got some castrol edge 10w-30 and got an oilchange. But the oil sign started coming on at idle and in traffic even then.
My friend thinks its the engine oil cooler, its unable to cool the engine oil when my car is idling. Last 2 weeks apart from the oil sign my engine temperature is rising to 3/4ths up the gauge and even if i let the car idle for 10 mins before shutting it down, it doesnt cool down. The temperature only comes down while driving at speeds over 50 mph with no car in front of me. If there were traffic or a car in front of me(even if it were 40-60 ft away), temp reaches 3/4th of the gauge even while driving.
A second problem is that about 10 minutes of driving my battery and brake sign come on; they both keep disappearing and reappearing for a few seconds and finally come back on and then stay on till car is turned off. A few months ago my friend had mentioned that my battery cable was corroding and he fixed it temporarily. Could that be it or is it something else.

 

Wow...

I'd start with verifying that your cooling fans are working correctly, both on low speed and high speed.

Then I'd check the alternator output voltage at the alternator and the battery.

Then I'd replace the oil pressure sender first. If that doesn't help with the oil pressure signal, I'd have the oil pressure checked professionally. Might be time for an oil pump...

 

Thanks for replying.
The radiator fans do come on, especially at idle when the temp reaches 3/4 gauge. The temp then comes close to middle of gauge(a bit above halfway) and starts rising again to 3/4th gauge. I didnt know there was a low speed and a high speed for radiator fans. Will get back to you.