I know there are tons of threads about low oil pressure and what not, but I wanted to know for sure what you guys think about my situation. I have a 95 Z28 6-speed, everything stock, that recently started having problems. When I crank the car, the oil pressure is good...around 50 or 60 psi. When it gets warm it goes down to 10 at idle (just above the red line but never in the red) but back to around 20 or 30 when cruising . I can hear a slight tick/knock near the rear of the engine that just started when the oil pressure problem started. I've already changed the oil pressure sending unit so I'm pretty sure the pressure reading is correct. Its also leaking a little bit of oil at the rear of the engine in front of the transmission. I've been told it can either be one or a combination of: bad oil pump, rear main seal, or rear main bearing. Does this sound right? I don't want to pull the transmission and worry about dropping the oil pan if i dont have to. Thanks in advance.

 

Thats the same pressure mine holds, always has. I got it with 55k on the clock.

 

If the drop in oil pressure and the engine starting to knock occurred at the same time, I would be concerned about something going on with the bearings. If it was me I would send out an oil sample to a test lab for analysis. Well worth the $20 or so that it costs.

 

A knock and a tick are two different things. A bearing knock is a deep sound. Oil drips from gaskets are not going to decrease oil pressure. Not saying your oil pressure is great, but it is somewhat normal for an LT1 with some miles on it. A factor in oiling and bearing problems in the high mile engines is sustained high RPMs.

 

It's definitely a knock coming from the engine. It's not too loud but it's not a normal sound. It started about 2 weeks ago and I haven't driven it much since then. Before then, my oil pressure never went below 20. I've changed the oil since then and the oil looked normal (no trash in it). And, the mileage is just under 100K.

 

You can't always detect bearing metals (or other contaminants) in the oil by visual inspection. That's why I'm a firm believer in oil analysis.

 

a knock and low pressure can both be caused by a bad bearing, try a little thicker weight oil and see if the problem goes away

 

So should I not be concerned that driving it may mess up the engine internals? If I use thicker oil and it helps the oil pressure but the bearing is still bad, how long can I expect to drive it?

 

Until the bearing fails. Seriously, no one could predict that.