Corvettta

I was wondering if folks in this forum have ever wondered if their oil pressure gauges were actually 'fake'.

I find it hard to believe that my oil pressure is indeed always around 40 psi as the gauge seems to say, all the time, maybe close to 50 at speed and maybe just under 40 at idle.

I have owned many cars with oil pressure gauges and usually, the pressure at idle is around 5 to 15 psi when the engine is hot.

I believe that that in order to keep overzealous customers from complaining to the dealer that their car's oil pressure is lower than what they think it should be, GM calibrated the gauge to always be around the middle of the range unless there is truly a problem.

So basically, our oil pressure gauge is a mechanical idiot light.

EVRose

I don't think that's true. It says in the manual it could read as low as 6psi during long extended idle on hot days. If it were rigged the DIC would have to be fake too. We just have tight engines with good pressure.

Corvettta

I think the DIC is as fake as the oil pressure gauge. It's not about it being a tight engine, 40 PSI at idle when warm is simply too high and it only goes up to 50 when revving. If you do a search on the web about 'fake oil pressure' you will see that most, if not all modern cars have these fake oil pressure gauges as a means of keeping oil pressure complaints from customers who don't know any better down. Apparently many customers get nervous if they see their oil pressure go down when the car idles.

I know Mazda Miatas changed from 1993 to 1994 from a feal oil pressure gauge to a fake one and the subject is also covered in the Mercury Marauder forum.

One of these days, I would like to attach a real pressure gauge and see what the pressure really is.

EVRose

Or you could just drain the oil, start the car and see what the pressure is then.

Gearhead Jim

When the oil is cold, our 2009 will show 40 psi or more at idle.

When the oil gets up to 250 or so, idle pressure drops down to around 20.

That doesn't sound fake to me.

Bill Dearborn

You must not have owned that many cars since if you owned an older Chevy you would have known a pressure in that range indicated incipient issues. On those cars anything below 30 meant you were looking at a new set of bearings. Only engine that could get by with those pressures at idle was the Olds V8 and its pressure read lower due to the relative locations of the pump and pressure sensor.

Bill

oldmansan

On this forum you learn who to listen to and who to disregard. Bill is definately on my "listen to" list.

If someone has definitive proof that the stock gauge oil pressure readings (or any gauge readings) are not accurate, I'd be extremely interested.

I would think if there was any truth to the alleged inaccuracies, the high-horsepower junkies would have pointed this out long ago.

San

Olddudesrule

What would account for the relative large differences being reported between owner, when our cars are fairly similar? I have an 07Z, stock displacement, with the only internal engine mod being a Katech 110 Torquer cam. I've run M1 5w/30, and now M1 0w-30, and run @ 65-70 lbs at cold idle, up to 80psi @ 2500 rpm cold, and @ 50-55 psi warm (oil at 170*). Now, I haven't owned the car during our AZ summers, so maybe the pressure then will drop significantly under those ambient temps.

I've always been taught, up to safe limits, higher oil pressure is a good thing, or at the very least, not a bad thing. This car just seems to run a higher overall pressure than other sports cars I've owned (my 01 Dodge Viper ran @ 50 cold, and @ 35-40 warm, and the 5.0 in my FFR Cobra ran @ 45-50 cold, and 30 hot).

I realize comparing other vehicles is apples and oranges, but I'm mainly confused about differences between Z's of relative "sameness".

Corvettta

Look just look around at other modern vehicle blogs and you will see that the trend is such that modern vehicles' oil pressure gauges are indeed set to always read in the middle zone to keep overzealous customers' nerves calm, they will only read in the red if there is indeed an issue.

I used to be an engineer at GM in the 90's and I remember this issue being discussed in an effort to reduce unwarranted customer complaints.

My old 1995 Firebird with an LT1 engine indeed showed much more variation in oil pressure as the engine moved from idle to its usual running rpm range than my Vette does and yes, the Firebird's engine was in perfect running order. I'm only saying that I find it odd that a Corvette at warm idle shows 40 psi and at 3500 rpm it shows 50. That is too small a range.

I would be interested to know if anyone has ever actually measured the oil pressure of an LS2 engine with a real oil pressure gauge.

DSOMC6

Mine reads very similar to this. I ran it pretty hard yesterday and looked down and saw 20psi on the gauge as it was cooling down at 70mph. I pulled-in just to verify I didn't have a oil leak.

Gearhead Jim

The dry sump engines read higher oil pressure than the normal wet sump, not sure if the relationship between hot and cold is different.

Gearhead Jim

You didn't say what you mean by "warm", but note that in my post #5 my oil at hot idle is only about half of what it is at cold idle. That sure doesn't sound like they are faking anything.

Our 2006 LS2 and now 2009 LS3 don't have an actual "red" zone, the Owner Manual says something like 20 to 80 psi is "normal" and the Service manual gives some other numbers at various rpm.