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Discussion Starter #1
I've just changed engine oil with filter as the summer is about to begin... Now the oil pressure gauge (before oil change) always went up to 40 Psi and staid there. Only under hard acceleration the gauge would go up to 50 Psi maybe.....

Now (after oil change) the gauge also stays around 40 Psi, but it's much more sensitive to even mild acceleration cycles, if pressed hard it goes up to 60 Psi, so I let it got (I was worried)... (the gauge goes up to 85 Psi, as you know of couse)... I don't believe, I overfilled new oil since oil level on dipstick isn't above the FULL mark....

I understand that oil pressure should oscillate but is this normal, any feedback appreciated....
 

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sasvod,

My car will idle at 35-40psi, but if I hit higher RPM's it shoots in to the 60's for me. I've never had a problem other than burning oil it seems - I am not sure if the burning is normal, it is a question im asking in another post lol

Overall though I think when my car was newer the pressure didnt go up as high, but im assuming two things: One is the engine breaks in and two, as I learn my car better I find I am more attentive to details than when I first got it. When I just got it I was a total n00b and completely overwhelmed of just owning and driving it lol.

Regards
 

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DC PIT CREW BOSS
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That is really not unusual but as a question. Did you change brand or weight of oil used?
 

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Discussion Starter #4
sorry didn't see you reposted...

well, I don't know which oil was used before I bought the car. Now I used Mobile 1 10w40 and I can tell, there IS a difference. Till now I kind of got used to higher meter fluctuation.
 

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Just curious...why such a "heavy" oil? Isn't 5W-30 the factory recommended weight?

I'm just guessing, but I'd say that could be why you're seeing higher pressure than before.

Scott
 

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Discussion Starter #6
hmm. could be.... I was told that 5w30 or 10w40 isn't much different. The difference is that 5w30 can be used in colder temperatures than 10w40. Oil becomes sooner more "liquid" at lower temperatures. Since I don't drive in winter it's no big deal....

but if this is the case, hmmm....

well today another weird thing happened to me. In the morning I went to work. I started the engine and "low oil level" message pops up. WTF? then I checked the dipstick and it said fine (just up to the full level mark). I thought maybe oil level sensor went broke. But then after driving a few miles suddenly oil pressure gauge showed noticable slump (about 1/3 lower then normal, I have kPa not PSI)... So I thing maybe there really isn't enough oil in the engine and the dipstick is a bit off or something ?!?

I'll add some oil to see what happens... I'll also check for any leaking too...
 

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I don't know how the oil level system works or the answer to this next question. Is there a oil filter bypass and could it be opening on cold start-up because of the heavier weight oil?
 

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Discussion Starter #8
hmm, never heard of such a bypass.... I'll check for leaks first, then add some more oil... What puzzles me is, that I changed oil 2 weeks ago, and there was no problem till today.... It's a sudden change... I'll check it today and repost what I found out...
 

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The dipstick is the ultimate oil level sensor. If it says full now, don't add anymore oil or you may really make yourself a problem.
 

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PRESSURE is a measure of RESISTANCE to FLOW
thicker or higher viscosity oils tend to RESIST the flow thru smaller clearances untill they warm up and the viscosity tends to drop off.
as long as the oil pressure stays above about 20 psi at idle and below about 80psi your NORMAL and should have no problems, but THINNER viscosity oils pump faster and reach the parts faster on start up where much of an engines WEAR occures, WITH SYNTHETIC OILS,THICKER oils DON,T, provide a big increase in protection as the FILM STRENGTH is similar, remember the object is to prevent DIRRECT mechanical contact thru having a FILM of oil under pressure BETWEEN the moving surfaces, the oils viscosity has little effect AS LONG AS its sufficiant to form that barrier FILM, and ABSORB AND CARRY AWAY HEAT,DEBRIE,(CRUD) from the bearing surfaces. modern synthetics DON,T THIN OUT under heat to nearly the same extent as mineral base oils did so thinner 5w30 and 10w30 can protect parts as well or better than 10w40,20w50mineral base oils that thinned out under high heat conditions
keep in mind the CLEARANCE between moving parts determines in part the load rates the oil film can support, as an engine wears it tends to have increased clearances so the resistance to flow drops slowly with wear.





if you want some further info, read thru these


http://www.bobistheoilguy.com/

http://www.performanceoiltechnology.com/tenmythsaboutsyntheticlubrication.htm

http://www.oil-tech.com/motoroil-comparison.htm

http://www.micapeak.com/info/oiled.html

http://minimopar.knizefamily.net/oilfilterstudy.html
 

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Discussion Starter #11
I didn't add any oil as the dipstick still showed full oil level mark..... And the low oil message also disappeared for good.... Though the pressure is still "unstable"....

I guess 10w40 vs 5w30 isn't recommended to change, next year 5w30 will be the end decision.....
 
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