Want To Try 30wt oils for the 1st time

[Jetronic]

Originally Posted By: alcyon
Cool, thanks for the peace of mind, I am still old school though. I will try to keep oil temps lower for this oil. The rise in oil pressure seems pretty good though. I am able to get 50PSI at 2500rpm at 90C bulk oil temp. with 5W-40 I get 60psi at same parameters.
I wonder if the PYB straight 30 will yield noticeably higher oil pressure.


The HTHS viscosity determines the PSI, so if I were you I'd just drive normally unless the pressure at idle drops to the 5 psi region, but it would need to get a lot warmer than 97°C to see that.

 

[Jetronic]

Originally Posted By: zeng
Quote:
One can have perfectly acceptable wear protection at a lower pressure since the flow is less restrictive and therefore more oil moving thru the pressure areas at a given temp.

At lower operating pressure, surely there can't be 'more' oil flow , given the reduced power input to the oil pump drawn from crankshaft.
JMHO.


the oil flow through the engine is determined by the RPM, unless the pressure equals 0 or the oil pressure relief is open.

 

[BrocLuno]

Originally Posted By: Jetronic
Originally Posted By: BrocLuno
I have run engines for tens of thousands of miles with 4~6 psi hot at idle. Not much of anything critical is happening then. Same engines made 40 psi at operating RPM at temp on a hot summer day pulling - good enough ...

Yeah, they were older somewhat tired engines - but they refused to die. Taught me that pressure was not an end goal in and of itself. Enough oil in the right places is the goal. Pressure is an artifact of system operation ...


Exactly. Hence 14 psi at hot idle being plenty to reach the rotest parts.

4 psi would be low to me as it could trigger the low pressure warning (0.3 bar or around 5 psi) and I don't have a pressure gauge. But as long as that doesn't happen at any time, I'm happy.



4 PSI was low and I had to change to an I-H oil pressure sender (3 PSI) so the light would stay off. As soon as the R's came up off idle, they were making more oil pressure. But these engines had a bazzillion miles on them and they kept right on trucking ...

 

[Shannow]

Originally Posted By: Jetronic


The HTHS viscosity determines the PSI, so if I were you I'd just drive normally unless the pressure at idle drops to the 5 psi region, but it would need to get a lot warmer than 97°C to see that.


Nit picking, but the HTHS/oil pressure thing is at high revs...

Here's the shear rates of (typical) engines.

for the mains and cams, can calculate the shear rate

Pi*D*RPM/(60*clearance)...remembering cam is half speed, and D and clearance are in the same units.

 

[zeng]

Originally Posted By: alcyon
Cool, thanks for the peace of mind, I am still old school though. I will try to keep oil temps lower for this oil. The rise in oil pressure seems pretty good though. I am able to get 50PSI at 2500rpm at 90C bulk oil temp. with 5W-40 I get 60psi at same parameters.
I wonder if the PYB straight 30 will yield noticeably higher oil pressure.

Assuming 2500 engine rpm at an oil pump flow rate of say 7 gpm (8.4 usgpm),pump power input into the above 5W40 and 10W30 oils would be 0.245 bhp and 0.204 bhp respectively, inclusive of noise energy.
10W30 has a power savings of 0.041 bhp (30 watt) out of an 80-90 hp engine,at reduced operating viscosity despite lower operating temperature by about 2*C ...... hence lower MOFT and wear protection.
I thought engineer always works towards lower operating temperature, to pre-empt viscosity thinning!
Originally Posted By: alcyon
My question is, is the 40wt too thick for my engine, causing intra fluid friction at the bearings, and increasing the heat at the bearings? If so, will going to a 30wt help to raise this equilibrium point to perhaps..4000rpm.
My Purpose is to delay this increase in heat of the oil to a higher rpm, and thereby reducing my bearing wear.

This engine may come with a 10W30 when new, but typically gets a OEM recommended 15W40 or 20W50 when aged from mechanics, with good reasons .... in Malaysia.
No, one reduces bearing wear by increasing operating viscosity/MOFT.
One doesn't reduce bearing wear with a reduced operating viscosity/MOFT!
Just my 2cents.

 

[Jetronic]

Originally Posted By: Shannow
Originally Posted By: Jetronic


The HTHS viscosity determines the PSI, so if I were you I'd just drive normally unless the pressure at idle drops to the 5 psi region, but it would need to get a lot warmer than 97°C to see that.


Nit picking, but the HTHS/oil pressure thing is at high revs...

Here's the shear rates of (typical) engines.

for the mains and cams, can calculate the shear rate

Pi*D*RPM/(60*clearance)...remembering cam is half speed, and D and clearance are in the same units.



Last night, in bed, where I get all my best ideas (just ask the wife) I was thinking I should have said the high shear rate viscosity at whatever the current situation is, but after that I thought it was close enough, and not as confusing...

 

[BrocLuno]

It does not seem that this engine is spending a ton of time at 5,000 RPM... If it's being operated prudently and is just in mid-life after a rebuild, the slightly lower viscosity being discussed here is well withing norms.

As long as there is enough film strength/thickness across the bearings, we're all good on that score. Other parts of the engine want other things. Ring pack and cylinder walls/piston skirts may want less VII's which your full synthetics were giving you in an off hand way. To find a really good multi-vis synthetic blend with low VII percentage is another good exercise in oil selection. Or just run a straight SAE 30 HD oil and be done with it

It's never going to be cold enough there to need a 10W anything ...

 

[alcyon]

I really wasn't happy with the performance of the Prestone 10W-30 , drove it for a week with low oil pressure which keeps going lower, and once temp reaches over 90 engine gets a little noisy. So i swapped out the 10W-30 last night and poured in almost 4qts of PYB 30 API SN. I started the car several hours ago and have a few observations. I hope i did not do any damage to my engine from driving it with the low 10W30 for 6 days.
Indeed oil pressure with this Straight 30 is much higher even at start up. The bypass seems to open at 90 psi, and for the first time with this oil, i am seeing the oil pressure go to 92psi on first start. But anyway this is to be expected. After the autochoke cut off at about 1 minute , i drove off, and indeed the gauge is giving a higher pressure than the previous 10W30. I have a feeling the 10W30 i bought isnt an ACEA A3/B4 oil even though labelled as one.
The warm up also seems a lot faster. At 90C i get a OP that is almost the same as a 5W-40 , at 20psi. Not bad at all !
I also feel a bit more drag with this oil. When the oil temp goes up to 92C the oil pressure does drop a bit . Since its a carb engine, the idle isnt so steady like a fuel injection engine, especially with the air cond on. Some times when the AC kicks in the rpm drops to bout 700 and stays there until i give a little blip then it goes to 1000rpm. At 700 the OP drops to about 10 psi. as soon as i blip the throttle and it settles at 1000 the OP goes to at least 18psi.

I notice also that the 5W40 gives a little higher OP at idle, but the engine is less likely to drop to 700 rpm when the AC kicks in, it usually drops to only 800rpm.
My theory is since the OP sensor reads the pressure before it enters the bearings, hence its not at a high shear area, the 5W40 is giving a reading of a 40wt oil pressure, but the viscosity at the bearings is actually lower due to the temporary shear of the VII, hence the feeling of less resistance.

For the straight 30 even though the OP reading is slightly lower than the 5W40, there is no temporary shear of the oil in the bearings, hence the feeling of higher drag.
Do i feel confident with the PYB 30 ? Yes I do, confident enough to run it to the full 10,000km OCI and submit a sample for UOA.
Do i feel sworn off VII loaded oils like 0W-40 or 5W-40 ? Cant say that for sure right now until i drive around more with this oil.
I do expect my mpg to take a slight dip though.

 

[Jetronic]

Do you have a link to a data sheet for the prestone? I think you could be right in your observation of it not being an A3/B4 oil.

But for Malaysia, I'd also go with a straight weight oil... except if you want slightly better efficiency, look for a real xw30 A3/4. PAO base oils will help in the situation you describe with the idle, due to the lower traction coefficient.

Same for the Phillipines, where 20°C is exceptionally cold and I hope to retire.

 

[Shannow]

Originally Posted By: alcyon
My theory is since the OP sensor reads the pressure before it enters the bearings, hence its not at a high shear area, the 5W40 is giving a reading of a 40wt oil pressure, but the viscosity at the bearings is actually lower due to the temporary shear of the VII, hence the feeling of less resistance.


The bearings, when operating in a high shear regime release oil at a rate commensurate with the HTHS, and draw it from the galleries at a rate sufficient to replace it.

The pump supplies excess volume, and as the bearings don't take it all, you see the difference as oil pressure.

The shear rate local to the sender doesn't change the pressure that you are seeing.

 

[zeng]

Originally Posted By: Shannow
The bearings, when operating in a high shear regime release oil at a rate commensurate with the HTHS, and draw it from the galleries at a rate sufficient to replace it.

Instead of operating low shear absolute viscosity, the HTHS in combination with rpm and load (besides Journal diam and clearance) shall determine the sommerfield no/specific MOFT?

 

[alcyon]

Originally Posted By: Jetronic
Do you have a link to a data sheet for the prestone? I think you could be right in your observation of it not being an A3/B4 oil.

But for Malaysia, I'd also go with a straight weight oil... except if you want slightly better efficiency, look for a real xw30 A3/4. PAO base oils will help in the situation you describe with the idle, due to the lower traction coefficient.

Same for the Phillipines, where 20°C is exceptionally cold and I hope to retire.


I have been trying to locate spec sheet for quite some time. No luck. I heard they have since folded their oil business here.

 

[BrocLuno]

Yeah 30, no VII's and the bearings will be happy

 

[Shannow]

Originally Posted By: zeng
Originally Posted By: Shannow
The bearings, when operating in a high shear regime release oil at a rate commensurate with the HTHS, and draw it from the galleries at a rate sufficient to replace it.

Instead of operating low shear absolute viscosity, the HTHS in combination with rpm and load (besides Journal diam and clearance) shall determine the sommerfield no/specific MOFT?


Yep,
all the charts are based on Newtonian oils, where the high shear and low shear are the same.

In spite of the above regarding oil pressure, I believe that the High shear viscosity should be used for MOFT, as the oil film itself is almost certainly high shear rates even if the area around the feed holes is still in low shear.

 

[zeng]

Originally Posted By: Shannow
all the charts are based on Newtonian oils,
I believe that the High shear viscosity should be used for MOFT.
Oops .....I'd been errorneously referring to operating viscosity (low shear), instead of operating viscosity(high shear) in VII'ed lubricants in assessing MOFT for components wear protection and durability.
Thanks for the heads up.

 

[Shannow]

Yeah, I've been struggling with that in gear oils.

The AGMA charts are for high VI oils that don't suffer from temporary thinning.

I'm still after my holy grail High Shear Viscosity Index.

 

[Ducked]

Originally Posted By: Miller88
Originally Posted By: Shannow
Originally Posted By: Miller88
I think it's a reasonable thought to run a 30 grade oil. However, I'm guessing there are some here that will advise you to stick with the 20w50 or go even heavier.


You've posted that same comment many times in many threads...got any names ?


Do I need to post names? Look at any "What oil should I use" thread. There's a ton of people who will recommend absurdly heavy oil.


You can have my name.

In what I'd guess is a similar climate to the OP, I have run 20W50, straight 40, and 15W40. Currently I'm on an accidental blend of straight 40 and 15W40. I'm not exactly recommending it, though, its just what I do. Manual (1987) says 10W30.

I'm seeking to minimise wear. A slight fuel consumption penalty is acceptable.

I havn't seen anything on here that invalidates this approach, or if I have, then I didn't understand (or perhaps didn't believe) it.

 

[zeng]

Originally Posted By: Ducked
Originally Posted By: Miller88
Originally Posted By: Shannow
Originally Posted By: Miller88
I think it's a reasonable thought to run a 30 grade oil. However, I'm guessing there are some here that will advise you to stick with the 20w50 or go even heavier.


You've posted that same comment many times in many threads...got any names ?


Do I need to post names? Look at any "What oil should I use" thread. There's a ton of people who will recommend absurdly heavy oil.


You can have my name.

In what I'd guess is a similar climate to the OP, I have run 20W50, straight 40, and 15W40. Currently I'm on an accidental blend of straight 40 and 15W40. I'm not exactly recommending it, though, its just what I do. Manual (1987) says 10W30.

I'm seeking to minimise wear. A slight fuel consumption penalty is acceptable.

I havn't seen anything on here that invalidates this approach, or if I have, then I didn't understand (or perhaps didn't believe) it.

It's absolutely absurd to equate 20W50 engine oils as 'absurdly heavy oil'.

I'm yet to hear from local mechanics and service guys suggesting an engine blew up due to use of 20W50.
Instead, half-dead engines with high oil consumption are always fed with 20W50..... as a band aid.

 

[BrocLuno]

Outside of the USA (Redline excepted) there are plenty of 10W-60 and 20W-70 oils available. I'd call a 70 kinda heavy for anything other than the Sahara...

Refiners would not be making these oils if they did not sell. So there is a market.

By comparison, a 20W-50 is mid-pak at best. 15W-40 is getting to the light side. And a 10W-30 is considered quite a light oil ...

My guess is those buyers do not spend any time here on BITOG

 

[zeng]

Quote:
It's absolutely absurd to equate 20W50 engine oils as 'absurdly heavy oil'.

I'm yet to hear from local mechanics and service guys suggesting an engine blew up due to use of 20W50.
Instead, half-dead engines with high oil consumption are always fed with 20W50..... as a band aid.

On 'absurdly heavy oil' and 'antiquated oil' like a 20W50 --
http://www.bobistheoilguy.com/forums/ubb...ell#Post4170887
Credit to FordCapriDriver.