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Old 07-05-2005, 02:13 PM   #1
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Default Oil Weight

I'm trying to decifer advantages and disadvantages to using higher weight oil. Everyone brags about having good oil pressure. But mine is always low. And it seems that most other'* oil pressure increses with RPM, but mine never does. It'* always stable, and when I first got the car running, it was at 45PSI, but right around when the head gasket blew, it was around 39PSI. Now, I realize the head gasket blowing could very well have played a role in the oil pressure drop, however the car has always had 40-45PSI oil pressure. And it never would increase with RPM. I use 5W-30 oil. But, I think I want to try 10W-40. I think maybe the extra weight with higher temps may help a little with engine protection. However, I live in Michigan, so I live in a cold climate, and I buy my oil by the case. So I would rather not switch between weights. I want one that can handle everything.

I also realize that oil filters have a bypass valve for when the pressure is too high and the filter cannot handle the flow, so when the weather is cold, I could still run 10W-40 taking advantage to that bypass valve? Or would it always be bypassing the filter until the engine is up to temp?


-justin
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Old 07-05-2005, 02:30 PM   #2
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Default Re: Oil Weight

Quote:
Originally Posted by opensourceguy
I'm trying to decifer advantages and disadvantages to using higher weight oil. Everyone brags about having good oil pressure. But mine is always low. And it seems that most other'* oil pressure increses with RPM, but mine never does. It'* always stable, and when I first got the car running, it was at 45PSI, but right around when the head gasket blew, it was around 39PSI. Now, I realize the head gasket blowing could very well have played a role in the oil pressure drop, however the car has always had 40-45PSI oil pressure. And it never would increase with RPM. I use 5W-30 oil. But, I think I want to try 10W-40. I think maybe the extra weight with higher temps may help a little with engine protection. However, I live in Michigan, so I live in a cold climate, and I buy my oil by the case. So I would rather not switch between weights. I want one that can handle everything.

I also realize that oil filters have a bypass valve for when the pressure is too high and the filter cannot handle the flow, so when the weather is cold, I could still run 10W-40 taking advantage to that bypass valve? Or would it always be bypassing the filter until the engine is up to temp?


-justin
your oil pressure is just fine... leave it be. i'm running a constant 45 psi or so in mine, a wee bit more when cold. but since I moved to full synth, it'* pretty solid. stick with the 5-30 unless you actually have a problem with it...
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Old 07-05-2005, 02:49 PM   #3
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I live in Michigan and I run 10w30 year round. Haven't had any problems with it yet...
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Old 07-05-2005, 02:56 PM   #4
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What does your oil filler cap say on it that you should use? Mine says 10-30 but 45 pounds is fine. My 95 gets down around 20 at idle when it is warmed up. The 97 doesn't go below 30 when warmed up.
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Old 07-05-2005, 03:12 PM   #5
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5W-30 everywhere [oil cap, owners manual, FSM].

I know it is in an acceptable range, but i'm not sure why it doesn't increase with RPM like a lot of other members. Could it possible be something up with my oiling system?


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Old 07-05-2005, 03:14 PM   #6
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Quote:
Originally Posted by BillBost37
What does your oil filler cap say on it that you should use? Mine says 10-30 but 45 pounds is fine. My 95 gets down around 20 at idle when it is warmed up. The 97 doesn't go below 30 when warmed up.
Agreed... Used 10w30 in the 89 bonnie.... If you read ther owners manual I think it actually sdays not to use 10w40...

My 91 usually hot idles at 35 Psi, at road speed its 50-60

the 95 hot idles between 30-35 and is at 60 at roadspeed...

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Old 07-05-2005, 03:22 PM   #7
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I'm running 10w-30, and my oil pressure never drops below 1/2 on the guage. It also goes nuts on WOT runs and increases with RPM'*. I always though there was something wrong with the guage, but I guess it'* a good thing. To my knowledge this engine has never had any major work done, just the tranny.
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Old 07-05-2005, 03:48 PM   #8
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captain: when you say nuts, do you mean erratic, or increases significantly? If it is the latter, what is your WOT pressure?

Okay, 10w-30, not 10w-40..


-justin
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Old 07-05-2005, 03:55 PM   #9
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It slowly climbs, then at about 4500RPM'* it goes right up, and then starts declining. Some times it bounces around really high as well.

Just a first gear run - http://members.shaw.ca/bonneville01/MVI_0007.avi

BTW, if anyone knows how to stop my turn signal indicator from coming on with the head lights, be my guest....
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Old 07-05-2005, 04:02 PM   #10
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captain: that is sweet! I wish mine would do that! lol [and i'm talking about the oil pressure]. Hardcore **** man. That'* what I am going to aspire to. What kind of oil filter do you use?


-justin
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