[GuardsRedCoupe]

Usually, my oil pressure meter stays between the 4 and 5 notches, no matter what. Today, however, it was varying with the RPM, and was dropping as low as the 2 notch when sitting idle. What it should it be reading, and is there a problem? Thanks!

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[SILVY968]

I run at 2.0 bars at idle when the engine is warm. 4ish bars the rest of the time.

The manual says @ 5,000 rpm @ normal operating temp of 90 degrees C, the pressure should be approx. 4 bars. It also says that @ idle with hot oil, pressure can sink as low as 0.5 bar...with no problems for the engine.

Your numbers are within the normal range.



Brian

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[Anchorman]

Agreed - what you describe is also what I see on my car. No worries.

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[GuardsRedCoupe]

Thanks for the info! That makes me feel better. <img src="/forum/images/smilies/968/biggrin.gif" class="smilie" alt="" /> Perhaps I should have been concerned earlier when it was between 4 and 5 all the time! I wonder what would cause it to do that. Ideas? <img src="/forum/images/smilies/968/huh.gif" class="smilie" alt="" />

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[968bill]

[quote name='GuardsRedCoupe' date='Mar 12 2006, 08:36 AM']Thanks for the info!  That makes me feel better.  <img src="/forum/images/smilies/968/biggrin.gif" class="smilie" alt="" />  Perhaps I should have been concerned earlier when it was between 4 and 5 all the time!  I wonder what would cause it to do that.  Ideas?  <img src="/forum/images/smilies/968/huh.gif" class="smilie" alt="" /> 

- Jon Hanson

[right][post="17233"]<{POST_SNAPBACK}>[/post][/right][/quote]

Oil level too high.

When I picked up my new-to-me '93 the oil level on the dipstick was apx 1/4" above the full mark when fully warm (and I hate that!) and it ran at 4 - 5 bars all the time. As soon as I got it home I dropped enough oil out to drop the level down to about 1/8" below the full mark and it now fluctuates between 3 and 4.5+.



For the record, I would much rather run with the oil level 3/4 qt. below the FULL mark than 1/4 qt. above the full mark. I believe it's easier on the oil seals and other parts that way.

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[flash]

me too bill



disclaimer time - i do not recommend this!



the car runs a little faster with a little less oil too - less drag on the rods going through - old street stock 1/4 miler trick - run a quart low



you could do it because it was only 1/4 mile, and no turns to starve things - then you would add the quart to go home

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[odb812]

i'm about the same, around 2 bars at idle when it's hot and up to 5 bars when it's above idle. what types of oil and weights are you guys using?

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[S_Cal968]

Oil pressure has more to with bearing clearances and viscosity then oil level. These engines carry so much oil, they don't necessarily have to be at the full mark. Although, as most know, the oil is partly responsible for cooling.



Another way to get more power is to run a lower viscosity, unfortunately the downside is less protection & higher wear.

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[flash]

yeah - that one is kind of spooky for me - i've actually seen bearings spin dry on 1/4 miles cars when doing that - just for a second, but that was all it took - we had a blown 20R do that at 9k - not pretty

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[968bill]

[quote name='S_Cal968' date='Mar 12 2006, 02:26 PM']Oil pressure has more to with bearing clearances and viscosity then oil level. These engines carry so much oil, they don't necessarily have to be at the full mark. Although, as most know, the oil is partly responsible for cooling. 

[right][post="17246"]<{POST_SNAPBACK}>[/post][/right][/quote]

While I would not disagree about the bearing clearances I do believe the oil level does have an impact on the pressure and so does viscosity and these are 2 very easy factors for us as owners to to adjust, even if we don't do our own work.



To clarify my previous statement, I always shoot for 1/2 qt. low when refilling my oil after an oil change and top it up to about 1/4 qt low after a day or so and leave it like that, it's better than overfilling. Except on the 911 that is, on the 3.2L's you want to keep them half way between the add and full mark, if you try to keep it at the full mark you will always be adding oil, they tend to burn off the top half and mine is no exception. It will stay at the 1/2 mark for 3k mi. until I change it.

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[frank moran]

[quote name='968bill' date='Mar 12 2006, 09:38 PM']While I would not disagree about the bearing clearances I do believe the oil level does have an impact on the pressure and so does viscosity and these are 2 very easy factors for us as owners to to adjust, even if we don't do our own work.



To clarify my previous statement, I always shoot for 1/2 qt. low when refilling my oil after an oil change and top it up to about 1/4 qt low after a day or so and leave it like that, it's better than overfilling. Except on the 911 that is, on the 3.2L's you want to keep them half way between the add and full mark, if you try to keep it at the full mark you will always be adding oil, they tend to burn off the top half and mine is no exception. It will stay at the 1/2 mark for 3k mi. until I change it.

[right][post="17262"]<{POST_SNAPBACK}>[/post][/right][/quote]

You do need an adequate supply of oil, oil pressure is the direct result of bearing clearance and of course a pump that can move the oil through the engine. The bearing clearance is the resistance to flow that gives the pressure reading. if you open the clearances up the pressure will drop, heavier oil will make up a bit of pressure but clearance is the key factor. The heavier oil trade off is a longer time to get oil to the vital parts on a cold morning..... Your only looking at between .0015 to about .003 clearance, once the bearings are completely worn out or damaged (dirt or lack of a supply of oil) the pressure will drop, and there is no sound repair other then new properly fitted bearings on a perfectly round crank journal. My engine idle's at a bit over 2 bar which is about 30 lbs. touch the throttle and it climbs up close to 5 bar....

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[SILVY968]

[quote name='odb812' date='Mar 12 2006, 12:10 PM']i'm about the same, around 2 bars at idle when it's hot and up to 5 bars when it's above idle.  what types of oil and weights are you guys using?

[right][post="17242"]<{POST_SNAPBACK}>[/post][/right][/quote]





I am running 20W 50 Royal purple synthetic.



FYI, 1 bar = 1 atmosphere pressure at sea level. 1bar = 14.5037738 pounds per square inch



2 bar = 29 PSI, 5 bar = 72.5 PSI

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[968bill]

[quote name='frank moran' date='Mar 12 2006, 10:05 PM']You do need an adequate supply of oil, oil pressure is the direct result of bearing clearance and of course a pump that can move the oil through the engine.  The bearing clearance is the resistance to flow that gives the pressure reading.  if you open the clearances up the pressure will drop, heavier oil will make up a bit of pressure but clearance is the key factor.  The heavier oil trade off is a longer time to get oil to the vital parts on a cold morning..... Your only looking at between .0015 to about .003 clearance, once the bearings are completely worn out or damaged (dirt or lack of a supply of oil) the pressure will drop, and there is no sound repair other then new properly fitted bearings on a perfectly round crank journal.  My engine idle's at a bit over 2 bar which is about 30 lbs. touch the throttle and it climbs up close to 5 bar....

[right][post="17267"]<{POST_SNAPBACK}>[/post][/right][/quote]

Yes, I agree with you. And we can make MINOR changes to the pressure the car runs at, change the bearing clearance, change the oil viscosity or change the oil level, 2 of the 3 are simple/easy to do but are NOT a substitute for replacing bad/failed bearings.



However, what started this discussion was (?) saying they were running 4 - 5 bars which I think we all agree is on the high side and the easiest/least involved check is to make sure your oil level is correct (not over full) and you're running the correct viscosity, checking bearing clearances is a little more involved and way above my pay grade.

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[Greimann]

[quote name='SILVY968' date='Mar 12 2006, 08:20 PM']2 bar = 29 PSI, 5 bar = 72.5 PSI

[right][post="17269"]<{POST_SNAPBACK}>[/post][/right][/quote]

6 bar = 1.0 DUI <img src="/forum/images/smilies/968/smile.gif" class="smilie" alt="" />

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[SILVY968]

If it's the right bar... 1=DUI.

Be careful in our classic 968's

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[968bill]

My sincere apologies, I just re-read Jon's original post.



[quote name='GuardsRedCoupe' date='Mar 11 2006, 10:48 PM']Usually, my oil pressure meter stays between the 4 and 5 notches, no matter what.  Today, however, it was varying with the RPM, and was dropping as low as the 2 notch when sitting idle.  What it should it be reading, and is there a problem?  Thanks!

[right][post="17225"]<{POST_SNAPBACK}>[/post][/right][/quote]

When I first read it I just saw the first part and thought his car was staying at 4 - 5 bars AT IDLE which is what mine was doing when it was 1/4 qt over full which is why I made my original comment about checking the oil level.



Jon, I'm not an expert and I don't play one on TV but I believe what you are describing is a very normal reading for a warm engine.



Again I apologize for trying to make an issue where none existed.

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