Just bought a 1998 Blazer LS w/83K on it.After warm up & on the highway,what is the normal reading the oil pressure gauge should be at?
Thanx!

What speed?

At 55 mph.
When it's at idle it's around 40~42

between 1/2 and 3/4

my 95 while driving at any speed, as long as im on the gas, it will be a notch above the middle(40) when stopped and idle, goes below half. 1/3 id say. that too low?

my 95 while driving at any speed, as long as im on the gas, it will be a notch above the middle(40) when stopped and idle, goes below half. 1/3 id say. that too low?

Yip, completely normal.

The norm would be about 30 - 40 at idle and 45 - 60 while driving.

Personally, I wouldn't run it this low, but the minimum while hot is:
1000 rpm..............6 psi
2000 rpm............18 psi
3000 rpm............24 psi

I have a 98 blazer. I was driving at about 85 wen my check engine soon light came on. There is no oil leak. The temperature stays normal. But i have no idea why the light came on.

Any other symptoms other than the check engine light? I presume you have low to no oil pressure if you're posting to this old thread. Check your oil level. If the stick is dry, you're burning oil. Then get a scanner and read the trouble code.

The other common problem is a loose gas cap. Check the o-ring for good seal.

Hope this helps!