rule of thumb...take the first two numbers of your RPMs when it gets past 4000.

The gauge is really there to tell you:

1. "HEY NO OIL PRESSURE"
or
2. "HEY THERE IS TOO MUCH PRESSURE"

 

How many miles on the motor? Could be anything from a bad sending unit, to worn bearings... (in which case, you gauge is NOT lying to you....)

 

They can be inaccurate like anything else made by man or machine.

 

my old old chevy blazer would read no oil presure....then when i hit the gas it would go too the moon ! could be worn sending unit but im guessing worn motor !....... its has around 200+ kms...... i check my oil its not low.....and theres no ticking or knocking

 

I am not entirely sure why, but, pre- 70's GM products had oil pressure sensors that would last forever...... Starting in about the 80's, changing your oil was a gamble on whether the crazy thing would work again afterwards.....

 

Fords have awefully low oil pressure.
But as far as sending units...
Different sending units have different ohm ranges. If you have the wrong one installed, it can read 0 psi at idle and then be pegged once the pressure comes up a little.

 

You got that right. I have heard of some of the old FE big block fords oil pressure being so low that the oil light would come on at idle. But that was just their nature. It never hurt them.

 

my rams oil pressure light does come on at idle !!!!!!!!