oil pressure gauge

[niceguypmp3]

It has been said on here multiple times that our TB's oil pressure gauge isn't an accurate reading of the oil pressure and that the ecm just calculates certain factors and then shows a calculated guesstimate for oil pressure. Does anyone know why GM did that? Has anyone put an actual oil pressure gauge on these 4.2? Does the normal reading go really low at idle once warm or something? i am trying to wrap my head around why in these modern times that they wouldn't want to display the actual oil pressure of an engine.

 

[TJBaker57]

It is stated in service manuals that at operating temperature with 5w-30 oil at 1200 rpm the normal oil pressure is 12 psi. Can you imagine the number of owners that would be bringing these trucks back to the dealer when they saw a reading of 12 psi or less at idle?

I do have a mechanical gauge added to my 2002 Trailblazer. It's a high mileage (286000+ miles) engine and when fully warmed up at idle I see 10 to 12 psi. Cold (say 30°F) I see 60 something at idle.

 

[niceguypmp3]

OMG that is terrible that it's that low once warmed up! With newer engines supposedly with such tighter tolerances, i find it hard to believe that GM was ok with that low of an oil pressure. But obviously it doesn't negatively effect these engines because look at how long they are lasting!!!

 

[Mooseman]

Another possible reason is that when cold and at higher RPM, it can produce almost 100 psi of pressure and the dash one only goes to 80. Even if they put in a 100 or 120 psi gauge, people would freak out seeing this at 90-100 on cold starts and then freak out some more at the low hot idle pressure.

 

[rchalmers3]

I don't think GM invented this trickery, or at least they are not alone in the deception.
Toyota did this in their Landcruisers: using a small circuit board that gave three gauge results (low, medium and kinda hi) instead of displaying the actual pressure. I'm sure many many other marques engage in the foolery.

I agree with Mooseman, the engineers must have been ordered by the sales department to create a dishonest gauge in order avoid panicking the vehicle owners. Or something like that.