Trouble choosing oil: spec 60-70psi by 3,000 RPMs

[Daigle]

Hello,
My factory service manual calls for:

"60-70psi by 3,000 RPMs"

this seems to be either really limiting my oil selection, or a crock of u know what written in a service manual 18 years ago.

its 2.4L 4cyl DOHC Nissan making about 375whp and reving to 7500, track duty and hard street driving. I geeked out reading the forum and decided i needed to run a thinner oil. i pulled out last seasons 10w40 Castrol GTX for some 10w30 GTX (missing some data from runinng the 40wt last year). heres what i got:

10w40
idle @ 220F = 18-20psi
idle @245F = 16psi
220F, 3k = ? (all i can recall is ~50 psi @ "cruising" on highway)
245F, 3k = ?
WOT MAX = 80-85psi

10w30
idle @ 220F = 18psi
idle @245F = 12-14psi
220F, 3k = 50-52psi
245F, 3k = ??
WOT MAX = 70psi

motor is a little quieter at startup and i think while warm idle. i may have noticed a slight cooling bennefit from the added flow but tough to say, its like 40F outside. Despite not reaching the pressure requirement from the book i still think its a pretty well suiting oil. ill be adding an oil cooler soon. im guessing it will drop my temps 20-30F and will then be an even better suited oil.


any thoughts for my rookieass? am i doing it wrong? am i on the right track? do i try a 20wt next? im just confused by the service manual spec.

 

[Donald]

Pick your oil by what is in the owners manual (temp compensated).

I would not choose oil to get to a certain oil pressure.

If you really want to evaluate the oil pressure get a mechanical test gauge to check the oil pressure. Do not trust the sender nor the gauge.

 

[Daigle]

but that is the exact opposite of what BOBs motor oil university teachings are instructing. Everything i read in the motor oil university specifically said to choose the oil that meets the factory reccomended pressures. if you recall, BOBs ferrari called for 75 psi at 7k and that is how he choose his oil.

the pressures im reporting are from a quality aftermarket gauge, they're accurate.

besides my motor is not factory... it produces 3 times the BHP it did out of the show room. the motor never even came with a turbo so operating temps arent even relevant to the factory intended use. my oils at least 60-80F hotter than a stock motor normal operating temp senario.

 

[Rand]

Originally Posted By: Daigle
but that is the exact opposite of what BOBs motor oil university teachings are instructing. Everything i read in the motor oil university specifically said to choose the oil that meets the factory reccomended pressures. if you recall, BOBs ferrari called for 75 psi at 7k and that is how he choose his oil.

the pressures im reporting are from a quality aftermarket gauge, they're accurate.

besides my motor is not factory... it produces 3 times the BHP it did out of the show room. the motor never even came with a turbo so operating temps arent even relevant to the factory intended use. my oils at least 60-80F hotter than a stock motor normal operating temp senario.


you mean the article by dr. haas?

that wasnt Bob.

 

[Daigle]

thanks for the correction.

so.... my oil...
i definitely am not looking for a spoon feeding. If theres a better procedure for determining best oil for MY appliaction please point me that way.

 

[Coprolite]

M1 0w-40

or maybe any HTO-06

 

[Brons2]

Obviously the factory specs are out the window with the modifications you have made to the engine. My question would be, what is the maximum oil temperature that this beast will see at the track? I would pick an oil based on that metric to ensure the health of your engine. If your oil temp gets to the 275-300 range I wouldn't think an OTC 10w30 dino would be a good choice. I personally would be leaning towards something like Redline with it's very high HT/HS ratings.
http://www.redlineoil.com/product.aspx?pid=4&pcid=21
3.8 HTHS, 6% noack.

If not that, then maybe RT6? Thicker, but available at Walmart.

As for the "spoon feeding" you refer to, opinions are going to be all over the place on this one.

 

[aquariuscsm]

What kind've Nissan is this?

 

[JGW]

I agree with the Redline recommendation.

 

[OVERKILL]

M1 15w50 is another choice and may get your oil pressure up into the right range.

 

[Daigle]

now were talkin! thanks

my normal temps are 220-240F street and 240-250F track... i usually just take a break at 250F and wait for 220F to come back around before my next run. i dont have to wait often though as you do wait in line. I know many track cars run up to 300F but i guess im just a wuss. i am about to install an oil cooler though so i anticipate new track temps of 220-230F.

do you think the 10w30 is appropriate for 250F though... i can definitely see it not being appropriate for 275-300.

I change my oil every 800-1000mi or every track day. my opposition to RL is the price as i am changing fluids often. I do however realize you gotta pay for the goods. i hoping to find an OTC oil that will work well when changed often.

lastly and im asking a lot here, but im not looking to run a defferent oil for the track. i want a compromise of oil for 200F and oil for 250F.

and its a 240sx

edit for the recent comment: ive ran rotella 15w40 before and thought it was a good oil, my pressures varied much less from temp than castrol. but i have a problem with the cold viscosity. this is a "race car" but its not some sponsored car getting new bearings every few races. it gets cold started and driven to work a few times a week. my question for you OVERKILLis where should my oil pressure be? i went from thicker to thinner for the bennefits of added flow, but you guys have me thinking otherwise.

 

[SwampSurvivor]

If Rotella 15w40 worked well except for the cold start, why not look into some of the 5W-40s on the market? Rotella T6 , M1 TDT, etc.

 

[OVERKILL]

Originally Posted By: Daigle
my question for you OVERKILLis where should my oil pressure be? i went from thicker to thinner for the bennefits of added flow, but you guys have me thinking otherwise.


Flow is flow. You have a positive displacement oil pump, unless the oil is being dumped out the bypass, it is seeing the same volume of oil. Pressure is resistance to flow through the system.

You should have the minimum recommended pressure as indicated in the FSM. If that is 60-70psi at 3,000RPM, then that's what you should be shooting for. That range of pressure values exists for a reason.

 

[Daigle]

well... i was, and am pretty partial to non synthetics. however now seeing that i can get sweet combos like 0w40 M1 i may have to switch to that or T6. cost is the main factor for using dino. i must also shamefully admit my rear main cover is leaking a tad and synthetic is going to make it worse. i dont want to pull the trans for a leak thats really not too bad. please dont read that as "cheap" ill spend $ on anythign that can be justified, but my OCI is 800-1000miles so it seems a waste to run some of these pricy oils.

0W40 M1 and T6 seemed to be the reccomendation for a turbo MX5 thread on here recently.

maybe i should be putting on my big boy pants and leaving the dino for my commuter car. are there any dino advocates on here that race with it?

a local pro racer using the same motor and car runs dino and just changes it 3 times a race day (road racing is much tougher on temps than drifting though)

 

[Daigle]

Originally Posted By: OVERKILL
Flow is flow. You have a positive displacement oil pump, unless the oil is being dumped out the bypass, it is seeing the same volume of oil. Pressure is resistance to flow through the system.


im a little confused by this comment, but sounds like your the guy to straighten me out. correct me if im wrong but for a given pump at a given rpm, a less viscous oil will have a greater volume of flow than a more viscous oil. assuming the bypass is not hit could we not say 10w30 flows more volume than 10w40? thats what school told me and Dr. whoever wrote the oil university stuff. i was under the impression i was after the thinnest oil possible that still met my factory requirements under my operating temps.

Originally Posted By: OVERKILL
You should have the minimum recommended pressure as indicated in the FSM. If that is 60-70psi at 3,000RPM, then that's what you should be shooting for. That range of pressure values exists for a reason.


it just seems odd that it calls for that much pressure so early... it worries me i'll hit the bypass shortly after (not sure what psi that is though). what it sounds like is im going to need a 50wt oil to get back to that spec for my operating temps. im almost positive 40wt did not get 60psi at 3k when hot (240F)

 

[OVERKILL]

Originally Posted By: Daigle

im a little confused by this comment, but sounds like your the guy to straighten me out. correct me if im wrong but for a given pump at a given rpm, a less viscous oil will have a greater volume of flow than a more viscous oil. assuming the bypass is not hit could we not say 10w30 flows more volume than 10w40? thats what school told me and Dr. whoever wrote the oil university stuff. i was under the impression i was after the thinnest oil possible that still met my factory requirements under my operating temps.


For every turn of the gears in a positive displacement pump, a given amount of oil is displaced. It doesn't matter if that oil is SAE50 or 0w-20.

What IS relevant is the role of the bypass, which is why I specifically mentioned it. Your oil system post-pump is essentially a fixed orifice. To move more volume through that orifice requires more pressure. The more pressure the greater the load on the pump of course, because that pump is displacing the same amount of oil every revolution. So in comes the role of the bypass to dump oil that, at a given pressure ceiling, cannot be forced into the rest of the engine.

Now, you can raise that pressure ceiling to force the engine into seeing greater oil volume at a greater pressure, but that, depending on application, can be wholly counter-productive.

Now, with a thinner lubricant, more oil can be pushed through the orifice before engaging the bypass. So for a given pressure (resistance to flow) you have more oil volume being pushed through the system.

Think of it this way (these are theoretical numbers):

at 3,000RPM your oil pump can move 3.2GPM of oil.

With 5w-40 this generates 60psi
with 5w-30 this generates 50psi

The engine is seeing the same volume of oil. But it requires more PRESSURE to move that volume of oil with the heavier grade.

What this means is that once you approach the limit of the bypass, a thinner lubricant will allow more oil volume to go through the engine before bypassing than a thicker oil.

However, if you aren't hitting the bypass, and you have a minimum oil pressure spec provided by the manufacturer, your goal should be to be above that spec by a safe margin.

Does that make sense?

Quote:

it just seems odd that it calls for that much pressure so early... it worries me i'll hit the bypass shortly after (not sure what psi that is though). what it sounds like is im going to need a 50wt oil to get back to that spec for my operating temps. im almost positive 40wt did not get 60psi at 3k when hot (240F)


It's not odd at all. Every oil system is different and has different requirements. That's why we have the FSM to give us these values

The Ford Windsor factory bypass is set at ~65psi. When cold, many of the engines would hit that on fast idle, LOL! Ford's minimum pressure spec was something like 10 or 15psi hot at idle. And something like 30psi by 3,000RPM. Much lower than yours. But with a pressure ceiling of 65psi, it makes sense, right?

My engines always were in the 30's hot at idle with an xW-30 in the sump. I was at ~38psi hot at idle on M1 0w-40 and on the bypass by 5K IIRC.

 

[Daigle]

uhhhhh that was AWESOME, thank you OVERKILL! you speak my language, i totally follow and REALLY appreciate you taking the time to type that up for me.

so i think i still have the same end goal then? (thinest oil that hits bypass the latest) but now have a better understanding of it. i have to do an oil change now so i think i will try a 0w40 or 5w40. last time i put synthetic in a car with iffy main seal it leaked though. boy do i not want to pull that transmission again lol.

i also NEED to find out the bypass pressure. I cant find it in the FSM and not even on a forum entirely deticated to my motor ka24de. what i do know is ive never seen the pressure go above 80-85 (15w40).

 

[OVERKILL]

Originally Posted By: Daigle
uhhhhh that was AWESOME, thank you OVERKILL! you speak my language, i totally follow and REALLY appreciate you taking the time to type that up for me.

so i think i still have the same end goal then? (thinest oil that hits bypass the latest) but now have a better understanding of it. i have to do an oil change now so i think i will try a 0w40 or 5w40. last time i put synthetic in a car with iffy main seal it leaked though. boy do i not want to pull that transmission again lol.

i also NEED to find out the bypass pressure. I cant find it in the FSM and not even on a forum entirely deticated to my motor ka24de. what i do know is ive never seen the pressure go above 80-85 (15w40).


I'd start with something like M1 15w-50 and see where you are at. You can always go down to a 5w-40, but I'd start heavier.

 

[Mitch Alsup]

Originally Posted By: Daigle
my normal temps are 220-240F street and 240-250F track... i usually just take a break at 250F and wait for 220F to come back around before my next run.


With those oil temps, you should not have to worry about going to a thicker or thinner oil.

 

[Daigle]

OVERKILL

maybe im perceiving a problem thats not there... but with 15wX (40 rotella dino) my motor was SUPER loud at cold start and idle in general, (10w30 was noticably quieter) and the pressures were so high i had to chang my driving behavior durring warm up driving. i also thought 90% of engine wear happens at startup and a thinner cold rated oil will help reduce that. are these concerns somewhat neglegable? of course i want my motor to run well and last as long as possible.


good to know MITCH! i was hoping it wasnt to big of a range for one oil.