Understanding Oil Pressure

[O Vette]

I have an '04. After starting the motor the oil pressure reads in the low 50's and after driving for 10-15 minutes it drops to about 42 psi. At start up, I suspect the oil pressure is higher because the oil is colder and thus thicker. As the oil warms it becomes less thick and thus the pressure drops. Am I correct my assumption? If not, why the drop when the oil heats up?

 

[XLR8]

Good question and I believe you're correct, though I don't recall if I've been told this or surmised it myself.

Someone more knowledgeable should be along soon to enlighten us both.
Jane Ann

 

[Hib Halverson]

I have an '04. After starting the motor the oil pressure reads in the low 50's and after driving for 10-15 minutes it drops to about 42 psi. At start up, I suspect the oil pressure is higher because the oil is colder and thus thicker. As the oil warms it becomes less thick and thus the pressure drops. Am I correct my assumption? If not, why the drop when the oil heats up?

Your assumption is correct.

 

[fixvet]

I have an '04. After starting the motor the oil pressure reads in the low 50's and after driving for 10-15 minutes it drops to about 42 psi. At start up, I suspect the oil pressure is higher because the oil is colder and thus thicker. As the oil warms it becomes less thick and thus the pressure drops. Am I correct my assumption? If not, why the drop when the oil heats up?

You got it, bro! I try to let my LS1 oil warm up to about 100deg/oil before backing out of the garage, especially if I haven't driven it for a week or so........which seldom ever happens though. Mine sets between 37 and 40 psi all day long when I'm on long road trips at 75mph, with the oil temp around 220-240.

 

[O Vette]

fixvet, your response leads to another question. I once read that it is not good to let a car idle excessively (5 or 10 minutes) after starting, expecially in cold weather, because the oil won't be distributed or splashed sufficienty for lubrication. Apparently, it was better to drive the car which would allow better oil distribution. That was some years ago, so, things may have changed. However, I don't think standard Vettes have oil pumps and I know they don't have dry sumps, so, perhaps it is still true.

 

[Mac]

fixvet, your response leads to another question. I once read that it is not good to let a car idle excessively (5 or 10 minutes) after starting, expecially in cold weather, because the oil won't be distributed or splashed sufficienty for lubrication. Apparently, it was better to drive the car which would allow better oil distribution. That was some years ago, so, things may have changed. However, I don't think standard Vettes have oil pumps and I know they don't have dry sumps, so, perhaps it is still true.

Standard Vette engines have oil pumps. The models with dry sumps have multiple oil pumps. Excessive idling might have been a problem in the past but with today's engines and oils, the only issue is the cost of fuel.

-Mac

 

[Hib Halverson]

Standard Vette engines have oil pumps. The models with dry sumps have multiple oil pumps. Excessive idling might have been a problem in the past but with today's engines and oils, the only issue is the cost of fuel.

-Mac

Mac is spot on. All Corvette engines have oil pumps. The dry sump engines have one pump but the pump has multiple stages and is thicker. This is why the crankshaft on LS3 manuals, LS7s and LS9s has a longer "snout".

With modern engines, any warm-up more than a several seconds simply wastes fuel.

That said, it is better to wait until the oil temp reaches 125 degrees or so before any wide open throttle operation.

 

[Red Vette]

Mac is spot on. All Corvette engines have oil pumps. The dry sump engines have one pump but the pump has multiple stages and is thicker. This is why the crankshaft on LS3 manuals, LS7s and LS9s has a longer "snout".

With modern engines, any warm-up more than a several seconds simply wastes fuel.

That said, it is better to wait until the oil temp reaches 125 degrees or so before any wide open throttle operation.

On Billy Rerickers Callaway, the instructions were to not to use WOT until the oil temp reaches 180 degrees. I assume that applies to all Callaways.
Barrett

 

[Mac]

On Billy Rerickers Callaway, the instructions were to not to use WOT until the oil temp reaches 180 degrees. I assume that applies to all Callaways.
Barrett

I wonder how they picked 180? Do they articulate a reason?

-Mac

 

[Vettehead Mikey]

I wonder how they picked 180? Do they articulate a reason?

-Mac

Most probably because oil temp is a better indicator of internal engine temp than the coolant .

Your advice about wasting fuel while letting a car warm up is spot on.

 

[Red Vette]

Sorry that I do not know the answer about the 180 degrees for the Callaway as Billy did not tell me. I believe that Vetthead Mikey's answer is probably correct. I know in the 1980s when the 300ZX turbos were having problems, it was because the engine oil was used to lube the turbo and when the driver stepped on the gas with a cold engine, there were problems as the oil did not get to the turbo.
Barrett

 

[Mac]

Sorry that I do not know the answer about the 180 degrees for the Callaway as Billy did not tell me. I believe that Vetthead Mikey's answer is probably correct. I know in the 1980s when the 300ZX turbos were having problems, it was because the engine oil was used to lube the turbo and when the driver stepped on the gas with a cold engine, there were problems as the oil did not get to the turbo.
Barrett

That sounds like a fairly serious design flaw to me. :ugh

-Mac

 

[ScottNoxid]

Vetthead Mikey's answer is probably correct.
Barrett

OK guys. Barrett should have said SPOT ON for his answer, and I see where WOT is used in place of Pedal to the Metal, but will someone explain to me how we Articulate a reason???????? Are we speaking the same language?????? confusedboogie

SC:WTT

 

[Mac]

Are we speaking the same language?????? confusedboogie

SC:WTT

That's the joy of English! So many ways to say the same thing.

In my case, Wide Open Throttle (WOT) is more accurate than Pedal to the Metal (PM) since my floor is fiberglass... Just saying....

-Mac

 

[billyz06-2003]

180 before wot

Sorry I did not pickup on this thread sooner. I happen to be talking to the head tech at callaway in new jearsy. The subject came up about how long before you can safely wot a 606 hp callaway. My answer was 180-190 temp. to be safe, I'm sure they know what they are talking about, so I always ahere to that.....................................Billy