5w 30 vs. 10w 30

[osheimer55]

would 5w 30 motor oil run at a lower PSI then 10w 30 motor oil? Becasue last time I did an oil change I used 5w 30 oil and now after my truck warms up and I drive to work when i stop at a stop sign or put my truck in park, my oil pressure drops down low, actually once my truck warms up the oil psi is a little lower then if I run 10w 30 like usual. Ive got a new high pressure oil pump, and new distributer.

[lesterl]

Could run lower, they are both 30 weight oils, the 5w has a lower startup viscosity than the 10w.....

[S15vortecpwr]

your problem is your high pressure pump. no stock motor needs a high pressure pump. I have a high volume pump in my 78 camaro and at idle with 10-60 BMW racing oil in it it idles at 12 psi and hits 75 at 3500 rpms.

It should not bother oil press since they are both 30wt as said. 5-10 wt is the startup flow rate. i woudl run 10-40 and be done with it. That what i run in all my trucks.

[SH-60B]

I think you would want to bump the higher number up to 40 and try that. The 5W and 10W are the winter viscosity of the oil, when the air temp and motor are cold. Your problem starts when the motor is warmed up, so I would look at the higher number. BTW, it's normal for the pressure to drop at idle with the truck warmed up. If it went below 10 PSI at idle I'd be concerned, but i would still like to see 20 at idle.

[osheimer55]

Thats what im saying, after it warms up, if I park it and leave it run at idle it drops down so low that the check guages light comes on. I mean, i havent had any problems with it, and its been doing it for a couple weeks now, so im just gonna change my oil in the next week or so to somthing thicker.

you guys suggest 10w-40?

[uhlhazard]

I have never seen the science behind running oil of a different weight than the manufacturer recommends for your climate on a stock engine.

If it was me, I would use the engineers ideas and run 5 or 10 w 30.

Also, the way oil is rated eg: 10W30 means when the engine is first started, the oil has a 30 weight. When it warms up it becomes the first number: 10 weight.

You guys are spreading misinformation and stating how multi-viscocity oil works positively wrong.

Google is your friend:

http://en.wikipedia.org/wiki/Motor_oil

Now for your oil pressure issue of: loss @ temperature. I would borrow/buy a mechanical oil pressure gauge and plug it into your car and compare its readings.

You most likely have a bad sending unit or cluster gauge.

Now if the mechanical gauge says you intermittently have no oil pressure then you obviously have a very serious issue. I have no experience with it personally so I will share with you what I know.

You could have a damaged oil pump or pickup tube.

Try the mechanical gauge and let us know how it worked out for ya.

I have 314K on my original 4.3 in my 96 pickup. It has had Castrol Syntec 5w30 since about 40K on the clock and changed every 5k (or longer) so thats my evidence to back up my belief in the engineers.

Yes I drive the shit out of it... and so should you.

[SH-60B]

Quote: Originally Posted by uhlhazard

I have never seen the science behind running oil of a different weight than the manufacturer recommends for your climate on a stock engine.
If it was me, I would use the engineers ideas and run 5 or 10 w 30.
Also, the way oil is rated eg: 10W30 means when the engine is first started, the oil has a 30 weight. When it warms up it becomes the first number: 10 weight.
You guys are spreading misinformation and stating how multi-viscocity oil works positively wrong.
Google is your friend:
http://en.wikipedia.org/wiki/Motor_oil
Now for your oil pressure issue of: loss @ temperature. I would borrow/buy a mechanical oil pressure gauge and plug it into your car and compare its readings.
You most likely have a bad sending unit or cluster gauge.
Now if the mechanical gauge says you intermittently have no oil pressure then you obviously have a very serious issue. I have no experience with it personally so I will share with you what I know.
You could have a damaged oil pump or pickup tube.
Try the mechanical gauge and let us know how it worked out for ya.
I have 314K on my original 4.3 in my 96 pickup. It has had Castrol Syntec 5w30 since about 40K on the clock and changed every 5k (or longer) so thats my evidence to back up my belief in the engineers.
Yes I drive the shit out of it... and so should you.

As far as the oil's weight, you have it pretty much backwards. With 10w-30, the oil flows at 10 grade when cold, and 30 grade when warmed up. It's basically a 10 weight oil that won't thin more than a 30 weight when warmed up.
It actually states that in the wiki link you posted. BTW, wikipedia is just an experiment. Anyone can add to it, no matter if the information is correct or not. Ironically, your "mis-information" comment applies to you.

[uhlhazard]

oil thins when heated.

Go outside when it is 10 degrees F and dump out a quart of oil.

Now do this @ 100 degrees F.

Got faster didn't it?

Don't tell the epa.

[Crew Cab Sonoma]

pour it into an empty container... so you dont get charged
with "enviromental crimes".....

[dimerunner88]

Quote: Originally Posted by uhlhazard

oil thins when heated.

Go outside when it is 10 degrees F and dump out a quart of oil.

Now do this @ 100 degrees F.

Got faster didn't it?

Don't tell the epa.

multi-viscocity oil doesn't work that way,it becomes thicker at higher temps. take some 0w-30 for example,its the thickness of water until you reach 150-200 degrees(the point when oil changes to the higher viscocity) then it becomes just like everyother 30 weight oil.

heres a site you can learn from
http://www.bobistheoilguy.com/forums/ubbthreads.php

[More Displacement]

Ok first off anybody that sites wikipedia must have flunked high school or passed by the skin of there teeth. Everybody knows anybody can get on wikipedia and write stuff. You say that the pressure drops slightly when you use 5W-30 instead? WHy did yo install a high volume oil pump in the first place? An oil pump wont fix internal problems. Most manuals come with a diagram that shows you temp vs oil viscosity.

[SH-60B]

Quote: Originally Posted by uhlhazard

oil thins when heated.

Go outside when it is 10 degrees F and dump out a quart of oil.

Now do this @ 100 degrees F.

Got faster didn't it?

Don't tell the epa.

LOL! The SAE labs use simulators to derive their figures. I didn't read the whole thing in the link you posted. You should read it yourself.

[osheimer55]

Whats the big deal with the high flow oil pump. More is better right? I just changed it because it was the origional and was convienent at the time. Ive had a manual guage on it before, im sure the pumps working.

[uhlhazard]

I don't know what to tell you guys. I sourced what I was taught. You have only berated my source and have none of your own to reference.

[More Displacement]

I would really like to know what the PSI numbers are exactly. Anything less than 10 psi is dangerous territory for an engine. Was the pressure fine before you changed the pump. Why was it convienent to change the pump? What else did you do?

[uhlhazard]

How come oil pressure drops after an engine is warm? Does it drop from the oil becoming thicker (30) weight or thinner (5/10) weight?

I genuinely am open to discussing this. I think it will help the original poster too if he can be satisfied on how the weight systems work.

[lesterl]

Oil pressure drops because as metal heats it expands and so do the clearances on bearings, thus loosing pressure from increased leakage between bearings.

[dimerunner88]

Quote: Originally Posted by lesterl

Oil pressure drops because as metal heats it expands and so do the clearances on bearings, thus loosing pressure from increased leakage between bearings.

yup, the metal expands with temperature thus increasing tolerances and bearing clearances.

[osheimer55]

so, your saying that my oil is more "free flowing" since the metal is expanding as the engine temp heats up, thus causing less oil pressure.

If im understanding what your saying then your saying that my oil is too thin when it heats up. So i should switch back to 10-30 like ive ran for 7 months without a problem after I switched my oil pump.

It was convienient at the time because when we swapped transmissions we did a oil pan gasket, and changed the pump.

I did however just do valve guide seals on my engine, and a head gasket. After I did that was when I put the 5w-30 in

[More Displacement]

Like other people have said at idle wether you run 10W-30 or 5W-30 when the engines hot both oils are at a viscosity of 30. Now im not positive what the oil change rate is, is it instantaneous at a certain temp or does it slowly get thicker. Now like I asked before what was your PSI reading with the 10W-30? If it was just above the point that the gauges turn on than Id say you have an issue that isnt oil related.

[lesterl]

If you try some new Rod and Main Bearings it is a good possibility your pressure would come up some.

And Yeah, I would put 10w30 back in it, even tho you still havent told us what year / engine you have.

[jherrell]

Quote: Originally Posted by osheimer55

Thats what im saying, after it warms up, if I park it and leave it run at idle it drops down so low that the check guages light comes on. I mean, i havent had any problems with it, and its been doing it for a couple weeks now, so im just gonna change my oil in the next week or so to somthing thicker.

you guys suggest 10w-40?

are you a 1/2 quart or more low? I've owned numerous S-10s over the past 15+ years, and all of my 4.3s would show a low oil pressure at idle warmed up if the oil level was just over a half quart low. Even on a brand new engine I have seen this.

[97s104x4]

with mobil 1 10w30 syn. i see 60psi at cold and 40 psi at warm, stock oil pump.

[osheimer55]

I have Mitchel on demand and this is the spec. table they have for oil psi in a 91 4.3 TBI engine (thats mine).
1000 RPMs-6psi
2000 RPMs-18psi
4000 RPMs 24psi
These are the minimum specifacations

Im sure its not my guage, or the pump. Because Im getting between 60-80psi when I start my truck up cold at idle, but after I drive to work (20 min ride at 50mph average) and the engine heats up is when my oil pressure is lower. It holds about 40psi driving anything above 20mph, but if I drive slow or stop and idle. It drops down low. But I bet its still higher then 6psi, its just the stock guages in my truck arent exactly precise lol.

[uhlhazard]

Probably the gauges, Mine is 60-70 psi depending on outside temp at startup idling. Driving it moves up roughly 5 psi. Once it gets warm it will run about 40psi when being driven and about 20 psi hot idling. If you get on it once it's warm the pressure will rise to about 50psi hot.

My fullsize does the exact same thing except once it is warm it does not change oil pressure.

This is all according to my admittedly low quality cluster readings. My full size now reads oil pressure about an additional 10 psi higher no matter what now. I guess 314K miles takes its toll.

[TA^Guy]

Quote: Originally Posted by uhlhazard

oil thins when heated.

Go outside when it is 10 degrees F and dump out a quart of oil.

Now do this @ 100 degrees F.

Got faster didn't it?

Don't tell the epa.

He's correct you have it backwards.

The first number is how the oil will flow when it's cold, the second number is how the oil protects when warm.

[SH-60B]

Quote: Originally Posted by uhlhazard

I don't know what to tell you guys. I sourced what I was taught. You have only berated my source and have none of your own to reference.

Here ya go -
http://auto.howstuffworks.com/fuel-e...estion1641.htm

http://www.motorcycleproject.com/mot.../motoroil.html

http://www.zddplus.com/TechBrief13%2...0Viscosity.pdf

http://www.avweb.com/news/maint/oil_..._197096-1.html

http://motorcycleinfo.calsci.com/Oils1.html

http://www.avweb.com/news/maint/oil_..._197096-1.html

It's a lot of reading, but you can get through it if you zero in on the parts dealing with viscosity. Learn from it and move on.

[uhlhazard]

Quote:

Another way of looking at multi-vis oils is to think of a 20W-50 as a 20 weight oil that will not thin more than a 50 weight would when hot.

Thanks for the excellent sources. I genuinely appreciate it.

They all say that multi viscocity oil thickens when it heats up. I thank you for your time and hope the people that think it works the other way will read this topic. Stupid wikipedia!

Again I stand corrected and thanks sh60b for taking the time to source everything!

[Crew Cab Sonoma]

there seems to be alot of mis-understanding about several things here.

first, oil does indeed thin out as it heats up. drastically...
multi-viscosity oils just dont thin out quite as much as
a comparable single/straight weight oil does,
lets say 10W-30, compared to a straight 10 weight oil.

second, hot vs. cold bearing clearances change very little.
not enough to significantly alter oil pressure.
as the crank/rod journals expand from heat, so do the
block/rod and bearings.

by far the single biggest reason oil pressure drops
in a hot engine, is because of the thinning out of
the oil when hot...


and third, how multi-vicosity oils are rated.
10W-30 does NOT mean its a 10 weight cold,
and 30 weight hot...

it means that the oil is a 10 weight "W" (cold) at 0 deg. F,
that wont thin out more an a straight 30 weight (cold)
rated oil would when heated to 200 deg. F...
NOT that it is a 30 weight oil when hot...

hope this helps straighten thnigs out some...

[uhlhazard]

So I am more confused now than ever before.

So when (10w30) oil is @ 100C it is 30 weight.

when (10w30) oil is @ 0C it is 10 weight.

To me it makes sense that oil thins when heated and it becomes thinner eg: 10 weight @ 100c and 30 weight at 0c.

But the previous posters have said I was incorrect.

I think what you are saying is that we are both wrong and that it is more of a middle ground. It seems we are missing some key information here.

[disturbing V6]

Quote: Originally Posted by Crew Cab Sonoma

there seems to be alot of mis-understanding about several things here.

first, oil does indeed thin out as it heats up. drastically...
multi-viscosity oils just dont thin out quite as much as
a comparable single/straight weight oil does,
lets say 10W-30, compared to a straight 10 weight oil.

second, hot vs. cold bearing clearances change very little.
not enough to significantly alter oil pressure.
as the crank/rod journals expand from heat, so do the
block/rod and bearings.

by far the single biggest reason oil pressure drops
in a hot engine, is because of the thinning out of
the oil when hot...


and third, how multi-vicosity oils are rated.
10W-30 does NOT mean its a 10 weight cold,
and 30 weight hot...

it means that the oil is a 10 weight "W" (cold) at 0 deg. F,
that wont thin out more an a straight 30 weight (cold)
rated oil would when heated to 200 deg. F...
NOT that it is a 30 weight oil when hot...

hope this helps straighten things out some...

I agree. Thats also the biggest reason in high performance engines to run a temp gauge on oil. Oil thins and looses viscosity drastically once it gets above 240+ degrees I believe is the temp for normal oil. Synthetics have a higher threshold before breaking down from the temp.Generally keeping it below 220 is the best. Also the old guages suck massively. Check the oil pressure with a after market bell and gauge to get a much better reading.

[Crew Cab Sonoma]

Quote: Originally Posted by uhlhazard

So I am more confused now than ever before.

So when (10w30) oil is @ 100C it is 30 weight.

when (10w30) oil is @ 0C it is 10 weight.

To me it makes sense that oil thins when heated and it becomes thinner eg: 10 weight @ 100c and 30 weight at 0c.

NO. both numbers still reference to the "cold" oil rating.

its not saying that 10W-30 is a 10 weight when hot,
its a 10 weight oil when COLD, that wont thin out more than
a 30 weight "COLD" rated oil would, when heated to 100 deg. C...
the rating doesnt give you an actual weight figure for
the HOT oil....

its a little confusing, but think about it for a bit and it'll
make sense.

[uhlhazard]

It appears that when you "assume" you make an ass outta u and me.

I assumed there was some hot/cold rating. There isn't one. This does give me an excellent excuse to wire up an oil temp sender though. God I love gauges.

[Crew Cab Sonoma]

an oil temp gauge will give you interesting lessons
in oil temps vs. coolant temps, and how much they
vary from each other...

[SH-60B]

Quote: Originally Posted by uhlhazard

So I am more confused now than ever before.

So when (10w30) oil is @ 100C it is 30 weight.

when (10w30) oil is @ 0C it is 10 weight.

To me it makes sense that oil thins when heated and it becomes thinner eg: 10 weight @ 100c and 30 weight at 0c.

But the previous posters have said I was incorrect.

I think what you are saying is that we are both wrong and that it is more of a middle ground. It seems we are missing some key information here.

Maybe it's the polymers that are confusing you.
http://auto.howstuffworks.com/fuel-e...estion1641.htm

At cold temperatures, the polymers are coiled up and allow the oil to flow as their low numbers indicate. As the oil warms up, the polymers begin to unwind into long chains that prevent the oil from thinning as much as it normally would. The result is that at 100 degrees C, the oil has thinned only as much as the higher viscosity number indicates. Another way of looking at multi-vis oils is to think of a 20W-50 as a 20 weight oil that will not thin more than a 50 weight would when hot

Why ask for sources if you aren't going to read them?

[patrickd45]

Quote: Originally Posted by dimerunner88

yup, the metal expands with temperature thus increasing tolerances and bearing clearances.

So what you are saying is that the rod ends and the bearings expand when they get hot and increase clearances, yet the crank journals do not expand too? I find that hard to believe. The metalurgists and engineers try hard to keep everything relative to avoid tight/loose conditions inside an engine.

Yes the 5 0r the 10 in the 5W30 is the cold wt and theoretically it won't thin past 30 wt when hot at what temp does it start thinning? Could be his engine is just running too hot

[Crew Cab Sonoma]

Quote: Originally Posted by jherrell

are you a 1/2 quart or more low? I've owned numerous S-10s over the past 15+ years, and all of my 4.3s would show a low oil pressure at idle warmed up if the oil level was just over a half quart low. Even on a brand new engine I have seen this.

i've deliberately ran mine almost 1 qt. low before, for track testing purposes, and never noticed a bit of difference in oil pressure. and certainly not at idle...

[uhlhazard]

No, I did read the sources and I am simply saying that I was wrong but I don't fully understand how exactly everything works.

I feel like we just opened an oily can of worms on my brain.

[cmitt]

Quote: Originally Posted by lesterl

Oil pressure drops because as meta l heats it expands and so do the clearances on bearings, thus loosing pressure from increased leakage between bearings.

I have a 96 blazer with the same prob idle@warm psi drops to 0. At first i thought it was a weak oil pump, but after changing oil pumps i had the same prob. I figured the bearings were shot so for a temperary fix I used some valvaline sae 50 racing oil and useing that and changing it every 5k miles It lasted another 30k miles then oil pressure just wouldn't stay above 10 psi at idle. Im in the process of swaping engines

[lesterl]

How about the regulator spring? IDR if it is in the pump or not.

[disturbing V6]

Heres a question for you guys did you check the pressure relief spring under the oil filter to make sure it is not stuck open. If it is it will allow pressure to drop.I know for a fact if it gets stuck open it drops pressure. Thats why the machine shop plugs it now in the race motor.

[osheimer55]

Well, I never heard of that spring, I wish i would have seen this yesterday as I jus changed my oil back to 10w-30. Needless to say, nothing changed.

Could you go into more detail about that spring?

Thanks

[lesterl]

Over pressure spring, when pressure gets to high, it bypasses and keeps the pressure under a certian point. Over time the spring, like any, can get weak and or break.

[BuckyBoy02]

Here's another excellent link explaining the chemistry behind oil viscosity ratings. Pretty much like the post by SH-60B, just another angle. Again it has to do with polymers and additives beyond the basic petroleum feedstock. Read down a ways to where it reads "The answer was (and is) multigrade! BTW, probably the best site on the web for anything oil related, is this site BOB Is the Oil Guy. Just type it in. It's not an individual person, but a complete oil engineering website composed of oil engineers, chemists, etc.. Lots of good info here. Maybe this will help clarify some confusion on the oil viscosity issue.

http://www.bobistheoilguy.com/forums...new=1 #UNREAD

[Crew Cab Sonoma]

Quote: Originally Posted by disturbing V6

Heres a question for you guys did you check the pressure relief spring under the oil filter to make sure it is not stuck open. If it is it will allow pressure to drop.I know for a fact if it gets stuck open it drops pressure. Thats why the machine shop plugs it now in the race motor.

thats not a pressure regulating valve under the filter.
its a bypass valve, incase a filter becomes clogged.
if anything, if it stuck open, oil pressure would actually
improve to a small degree. but you wouldnt be filtering
your oil near as well...

[dimerunner88]

Quote: Originally Posted by BuckyBoy02

Here's another excellent link explaining the chemistry behind oil viscosity ratings. Pretty much like the post by SH-60B, just another angle. Again it has to do with polymers and additives beyond the basic petroleum feedstock. Read down a ways to where it reads "The answer was (and is) multigrade! BTW, probably the best site on the web for anything oil related, is this site BOB Is the Oil Guy. Just type it in. It's not an individual person, but a complete oil engineering website composed of oil engineers, chemists, etc.. Lots of good info here. Maybe this will help clarify some confusion on the oil viscosity issue.

http://www.bobistheoilguy.com/forums...new=1 #UNREAD

yup,its a great vehicle maintenance site. i linked it in post #10

[BuckyBoy02]

dimerunner88: You're right. Sorry I missed your post.

[osheimer55]

So how should I go about checking that spring? And where is it in the oil cooler...top or bottom?

[jjimmy]

Wrong get on motor week’s website checkout Goss’s garage. Multi viscosity Oil has microscopic pieces of rubber, and other stuff added to the oil to modify its property. When the oil heats the rubber molecules expand thinning the oils viscosity. When it’s cold it’s at a low viscosity to aid in flow. As it warms it thins and the rubber expands to keep the viscosity up. If it were straight 10w oil it would flow like water at temperature. All fluids don’t act like water, for most fluids viscosity changes with temperature; water is virtually unique in its physical properties.

Quote: Originally Posted by uhlhazard

I have never seen the science behind running oil of a different weight than the manufacturer recommends for your climate on a stock engine.
If it was me, I would use the engineers ideas and run 5 or 10 w 30.
Also, the way oil is rated eg: 10W30 means when the engine is first started, the oil has a 30 weight. When it warms up it becomes the first number: 10 weight.
You guys are spreading misinformation and stating how multi-viscocity oil works positively wrong.
Google is your friend:
http://en.wikipedia.org/wiki/Motor_oil
Now for your oil pressure issue of: loss @ temperature. I would borrow/buy a mechanical oil pressure gauge and plug it into your car and compare its readings.
You most likely have a bad sending unit or cluster gauge.
Now if the mechanical gauge says you intermittently have no oil pressure then you obviously have a very serious issue. I have no experience with it personally so I will share with you what I know.
You could have a damaged oil pump or pickup tube.
Try the mechanical gauge and let us know how it worked out for ya.
I have 314K on my original 4.3 in my 96 pickup. It has had Castrol Syntec 5w30 since about 40K on the clock and changed every 5k (or longer) so thats my evidence to back up my belief in the engineers.
Yes I drive the shit out of it... and so should you.

[jjimmy]

my bad I ment to say thickening the oils viscosity when it warms up

Multi viscosity Oil has microscopic pieces of rubber, and other stuff added to the oil to modify its property. When the oil heats the rubber molecules expand THICKENING the oils viscosity

Quote: Originally Posted by jjimmy

Wrong get on motor week’s website checkout Goss’s garage. Multi viscosity Oil has microscopic pieces of rubber, and other stuff added to the oil to modify its property. When the oil heats the rubber molecules expand thinning the oils viscosity. When it’s cold it’s at a low viscosity to aid in flow. As it warms it thins and the rubber expands to keep the viscosity up. If it were straight 10w oil it would flow like water at temperature. All fluids don’t act like water, for most fluids viscosity changes with temperature; water is virtually unique in its physical properties.