Downside to Straight 50 weight for Harley Evo???

[ForestCat]

Hi,

I seem to remember hearing as a kid that heavier oil somehow "increases clearances". Probably just a myth...

In any case, I have a '97 Heritage Softail with 80ci Evo motor, 16k miles which seems to run well. However, once the engine/oil get good & hot, the mechanical (sewing machine) noise in the valve train, etc., seems excessive to me. If I won't be running the bike
Thanks for your opinions/expertise.

 

[Clevy]

Go ahead. The only downside would be cold start. If I lived in a hot climate such as Cali or Florida I'd use a straight grade no problem. I used Amsoil straight 60 and the only problem I have with it is cost. Bike ran fine with it last year in the dirty summer heat

 

[ammolab]

So it is noisy with a 20W-50 but quiet with a straight 50W?

Can some explain that to me?

 

[GhostFlame]

Look its a 97 harley. Its meant to rattle and shake. When its hot 50 w is 50w. With straight 50 you are sacrificing cold start pumping even at room temp. Your manual says 20 50 stick with that. Straight weights dont create larger gaps; they run okay in the larger tolerances of old pre 1975 ish engine design. Those engines were scrap at 70k-80k. Modern engines properly maintained
200000 , 300000 miles on the odo.
Dont do it.

 

[mene]

It is not a myth for me at least. Decades ago I rebuilded a Buick 215 (actually a Range Rover 3.5L) and used Rotella to break it in (back then it was just Rotella 30 weight) pressure was 55 PSI at idle after break in with oil at 95C; then smart as a 19 years old can be I switched to 20W50 and run it for 2500 miles didn't like it so switched back to Rotella, then pressure at idle went down to 35 PSI.

 

[ForestCat]

Ammolab, Please see here: http://www.v-twinforum.com/forums/engine-oils-lubrication/150802-50-straight-weight-miracle.html

Ghostflame, my manual DOES say to use 50 weight above 60 degrees. As to rattle/shake, I've had two other long-time HD owners say it sounds noisier than normal. The motor is whisper quiet until it gets hot & the oil thins out. In THEORY, 20-50 is 50 when hot, but in practice, I'm not convinced. See above link for a few real-world experiences. But, as you say, it's the cold starts, even in warm weather, that I worry about w/ straight 50. I'm not at all married to the idea, just seeking opinions like your own, which I do appreciate.

 

[ForestCat]

P.S. That thread gets serious again after a page or two of joking around, & others weigh in w/ similar experiences.

 

[Robenstein]

Well running a straight 50 will increase wear at startup over a 20w50 so it will create more clearance over time as the engine wears a little faster.

But I would say try a different 20w50. Some oils are just loud, and the EVO is just a loud engine. It is one of the reasons they went to chain drive cams in the Twin Cam, because of "noise pollution".

Just because an engine is louder with one oil does not mean it is lacking protection. Id try VR1 or Kendall GT1 20w50. Many say it those run quieter than some synthetics and do return great numbers in UOA's

 

[Clevy]

Op. I'm using rotella 15w-40 conventional in my Harley. Its modified and puts out 107hp/115tq. 100tq at 2200rpm.
I've tried every expensive big name oil out there. I really liked automotive RP 20w-50,red line 20w-50 and Amsoil 60 v-twin. The other 2 weren't bike oils.
I'm as happy with rotella as I was with those more expensive oils.
Lots of guys run a hdeo and their engines last just as long as those high priced oils.

 

[BusyLittleShop]

Originally Posted By: ForestCat
Hi,

I seem to remember hearing as a kid that heavier oil somehow "increases clearances". Probably just a myth...


Sounds plausible until you under stand that an increase in flow will increase clearances
and we know that a lighter flows more than a heavier oil...

If you wish to cut unwanted noise try a set of custom ear plugs...

Quote Dr Hass

"It is time to introduce the concept of lubrication. Most believe that
pressure = lubrication. This is false. Flow = lubrication. If pressure
was the thing that somehow lubricated your engine then we would all be
using 90 weight oil. Lubrication is used to separate moving parts, to
keep them from touching. There is a one to one relationship between
flow and separation. If you double the flow you will double the
separation pressure in a bearing. The pressure at the bearing entrance
is irrelevant."

"In fact the relationship between pressure and flow is in opposition.
If you change your oil to a thicker formula the pressure will go up.
It goes up because the resistance to flow is greater and in fact the
flow must go down in order for the pressure to go up. They are
inversely related. Conversely if you choose a thinner oil then the
pressure will go down. This can only occur if the flow has increased."


You're looking at custom molded ear plugs with tiny Sony digital
speakers... they cut 30db of wind noise and allow every note of the
music through even at low volumes... perfect...

 

[OVERKILL]

Originally Posted By: BusyLittleShop

Sounds plausible until you under stand that an increase in flow will increase clearances
and we know that a lighter flows more than a heavier oil...

If you wish to cut unwanted noise try a set of custom ear plugs...

Quote Dr Hass

"It is time to introduce the concept of lubrication. Most believe that
pressure = lubrication. This is false. Flow = lubrication. If pressure
was the thing that somehow lubricated your engine then we would all be
using 90 weight oil. Lubrication is used to separate moving parts, to
keep them from touching. There is a one to one relationship between
flow and separation. If you double the flow you will double the
separation pressure in a bearing. The pressure at the bearing entrance
is irrelevant."

"In fact the relationship between pressure and flow is in opposition.
If you change your oil to a thicker formula the pressure will go up.
It goes up because the resistance to flow is greater and in fact the
flow must go down in order for the pressure to go up. They are
inversely related. Conversely if you choose a thinner oil then the
pressure will go down. This can only occur if the flow has increased."




But you won't double flow.

Oil pumps are positive displacement (at least the automotive ones, I assume we aren't dealing with variable displacement pumps in a Harley....) which means that for every turn of the gears, they displace a given volume of oil. Whether that's at 5psi or 50psi, it doesn't matter, the same amount of oil goes through the pump.

Now what does play a role is of course the bypass on the pump. Once a certain head pressure is reached, a certain percentage of the oil goes out the bypass and not through the engine.

However, assuming we aren't on the bypass, 5w-20 or 5w-50, it doesn't matter, the engine sees the same volume of oil. The heavier oil will provide greater film thickness and not cool perhaps as well (run a few degrees hotter) and will, due to being thicker, generate more oil pressure (back-pressure), however VOLUME will be pretty much the exact same, and may even be HIGHER due to less leakage over the gears.

We had a neat discussion about this recently, if you want, I'll dig up the thread

 

[Clevy]

Originally Posted By: OVERKILL
Originally Posted By: BusyLittleShop

Sounds plausible until you under stand that an increase in flow will increase clearances
and we know that a lighter flows more than a heavier oil...

If you wish to cut unwanted noise try a set of custom ear plugs...

Quote Dr Hass

"It is time to introduce the concept of lubrication. Most believe that
pressure = lubrication. This is false. Flow = lubrication. If pressure
was the thing that somehow lubricated your engine then we would all be
using 90 weight oil. Lubrication is used to separate moving parts, to
keep them from touching. There is a one to one relationship between
flow and separation. If you double the flow you will double the
separation pressure in a bearing. The pressure at the bearing entrance
is irrelevant."

"In fact the relationship between pressure and flow is in opposition.
If you change your oil to a thicker formula the pressure will go up.
It goes up because the resistance to flow is greater and in fact the
flow must go down in order for the pressure to go up. They are
inversely related. Conversely if you choose a thinner oil then the
pressure will go down. This can only occur if the flow has increased."




But you won't double flow.

Oil pumps are positive displacement (at least the automotive ones, I assume we aren't dealing with variable displacement pumps in a Harley....) which means that for every turn of the gears, they displace a given volume of oil. Whether that's at 5psi or 50psi, it doesn't matter, the same amount of oil goes through the pump.

Now what does play a role is of course the bypass on the pump. Once a certain head pressure is reached, a certain percentage of the oil goes out the bypass and not through the engine.

However, assuming we aren't on the bypass, 5w-20 or 5w-50, it doesn't matter, the engine sees the same volume of oil. The heavier oil will provide greater film thickness and not cool perhaps as well (run a few degrees hotter) and will, due to being thicker, generate more oil pressure (back-pressure), however VOLUME will be pretty much the exact same, and may even be HIGHER due to less leakage over the gears.

We had a neat discussion about this recently, if you want, I'll dig up the thread

Well written.

 

[ForestCat]

"However, assuming we aren't on the bypass, 5w-20 or 5w-50, it doesn't matter, the engine sees the same volume of oil. The heavier oil will provide greater film thickness and not cool perhaps as well (run a few degrees hotter) and will, due to being thicker, generate more oil pressure (back-pressure), however VOLUME will be pretty much the exact same, and may even be HIGHER due to less leakage over the gears."

This has always been my understanding. What I had hoped to benefit from is the greater film thickness. But at this stage I'm leaning toward staying with 20-50, since I'm beginning to think the cold start penalties of 50 would offset any potential gains.

I do ride w/ good earplugs (for wind noise), and the engine noise per se is not bothersome to me, but it concerns me that the motor is slightly noisier than it should be. I'm totally in love w/ this bike & want it to last a good long time, so I want to do everything in my power to take extra good care of the engine, particularly re: lubrication.

I'll check out some of the oils mentioned here, some of which I've already read the good reports on in various forums.

 

[Shannow]

Originally Posted By: BusyLittleShop

Quote Dr Hass

"It is time to introduce the concept of lubrication. Most believe that
pressure = lubrication. This is false. Flow = lubrication. If pressure
was the thing that somehow lubricated your engine then we would all be
using 90 weight oil. Lubrication is used to separate moving parts, to
keep them from touching. There is a one to one relationship between
flow and separation. If you double the flow you will double the
separation pressure in a bearing. The pressure at the bearing entrance
is irrelevant."

"In fact the relationship between pressure and flow is in opposition.
If you change your oil to a thicker formula the pressure will go up.
It goes up because the resistance to flow is greater and in fact the
flow must go down in order for the pressure to go up. They are
inversely related. Conversely if you choose a thinner oil then the
pressure will go down. This can only occur if the flow has increased."


Flow isn't lubrication, and neither is pressure.

A bearing will have an amount of oil that stays in it doing the hydrodynamic lubrication function (film thickness), and each volume will stay in the bearing for a period of time, and some will be discharged from the side of the bearing (side leakage).

Different bearing designs have a different ratio of side leakage to recirculation. Large diameter, narrow bearings "leak" more of a percentage, small diameter wide bearings leak less of a percentage. More clearance on either equals more leakage.

More viscosity equals more film thickness...always.

Flow doesn't equal lubrication, as flow needs to be sufficient to make up for the amount of oil that makes it out the side. That is, to reach an equilibrium where enough is made up to replace that which is lost.

Pressure doesn't equal lubrication, as all that pressure does is to drive the flow into the bearings. In fact, bearings can actually "suck" on oil galleries, reducing the pressure locally to below atmospheric when they are pumping more out the sides than can be reasonably made up by pressure and flow restrictions.

Positive displacement pumps shift (largely) the same volume of oil with each revolution.

A higher oil pressure indicates that the pump is supplying more oil than the bearing leakage rate. A lower pressure is the converse.

 

[Silk]

A Harley should have a ball and roller bottom end, that's a serious amount of leakage, lots of flow and not much pressure, that noise is from somewhere else. Straight cut gears, primary drive, air cooling etc. My aircooled BMW is very noisy, I try not to have it running without my earplugs in and helmet on, otherwise I'd worry so much about the noise that I'd pull it apart....without my interference and using 20-50 it'll go for a long time yet.

 

[ForestCat]

"A higher oil pressure indicates that the pump is supplying more oil than the bearing leakage rate. A lower pressure is the converse."

Pretty much sums it up. While Harleys do have "real" (as opposed to plain) bearings in most of the engine, and, accordingly, tend to have much lower oil pressure, I just can't believe that more oil pressure (within reason, and all else equal) is a bad thing. I installed a Jagg six-row cooler on my Heritage, and my hot idle oil pressure has increased DRAMATICALLY.

It's hard to ignore the various "sewing machine" noises, but the motor is running wonderfully (albeit a touch lean, which I'm told is an Evo thing...) so I'll start doing oil analysis, and if that looks good, I'll try to stop worrying about it .

NOTE: I'm subscribed to this thread & have email notifications on, but not getting any. Any ideas?

 

[BusyLittleShop]

I think we agree that flow and pressure are inverse proportional
and what that always means is the relationship between pressure
and flow are in opposition... so if I use a heavy 50wt the
pressure will increase but the flow decreases compared to the
lighter 40wt where the flow will increase and pressure will decrease...

 

[splineman]

My Sportster 1200 with 50,000km on the clock is quite "noisy". Nothing sinister but not Honda quiet for sure.
I have used Penrite 20w-60, quite thick, and recently switched to Delvac 15w-40 on the advise and research done on this site.
I really cannot detect any difference in sound at around 190F oil temp, but the Delvac is noticeably thinner at cold.
Cheers

 

[Shannow]

Originally Posted By: BusyLittleShop
I think we agree that flow and pressure are inverse proportional
and what that always means is the relationship between pressure
and flow are in opposition... so if I use a heavy 50wt the
pressure will increase but the flow decreases compared to the
lighter 40wt where the flow will increase and pressure will decrease...


No, a positive displacement pump moves the same volume every revolution, regardless of the oil's viscosity.

 

[OVERKILL]

Originally Posted By: BusyLittleShop
I think we agree that flow and pressure are inverse proportional
and what that always means is the relationship between pressure
and flow are in opposition... so if I use a heavy 50wt the
pressure will increase but the flow decreases compared to the
lighter 40wt where the flow will increase and pressure will decrease...


You are thinking in terms of a situation like where you are using a fan and you block the fan, you increase the pressure observed after the fan blades but reduce the volume of air moved, correct?

That doesn't apply here due to the nature of a positive displacement pump. It doesn't care what you put in front of it in terms of resistance, it is going to move the same volume of fluid regardless. This is why we have bypasses. And why, in applications like the Ford Modular where the pump is high volume/high pressure, when the bypass gets stuck, it can cause the filter to explode. Because that pump is going to move that oil whether it's molasses or water, but the filter can't PASS the thick cold oil even with its own internal bypass wide-open and so the pressure in the system continues to climb due to the volume being shoved into it until something gives. In this case, it is the filter.

Think about a water hose with nothing on the end of it, the only restriction being the diameter of the hose. You have a positive displacement pump supplying that hose with water. Your argument about flow and pressure being inverse here doesn't work. If I spin the pump so that I observe 50psi at the pump where it feeds the hose and I spin the pump so that I observe 10psi at the interface that it feeds the hose, which scenario is going to result in more volume coming out the end of the hose? If flow and pressure were inversely proportional in this scenario then the 10psi at the pump should yield more flow. But it doesn't. Because I have to spin the pump SLOWER to see that 10psi, which means it displaces less volume per unit of time than if I were to spin it so that I'm observing 50psi. This is because with every rotation of the pump, it displaces a given volume of fluid and pressure observed after it is an indication of resistance downstream. As you increase volume, you increase pressure. A more viscous fluid will yield more resistance (back pressure) and higher pressure for a given volume. So 50psi with a fluid of 6.5cSt at 6gpm may, at the same pump rotational speed yield 55psi with a 9.0cSt fluid at 6gpm. In either case the pump is moving the same volume of fluid at the same RPM, the pressure observed is just indicative of the resistance downstream.