When to go up in viscosity because of wear?

[mene]

Originally Posted By: JAG
Originally Posted By: Warstud
Thicker oil increases pressure....decreases flow

Not true if neither the oil pump's bypass valve nor the oil filter's bypass valveopens loses since most automotive oil pumps are designed to pump a nearly constant volume of oil per revolution. Assuming no bypass valves are open and we are talking about hot oil (not highly viscous), a thicker oil will cause both higher oil pressure and higher flow rate, since oil pumps lose volumetric pumping efficiency as viscosity drops.

Original poster: how does oil consumption compare between M1 5W-50 and Amsoil ACD? Did you really use M1 5W-50 and not 15W-50? I ask because the former has been very hard to find in the U.S.


Hi JAG, Yes I used 5W50 and not 15W50 it was easy to find until about 1 1/2 years ago then it became increasingly hard to find until it was gone from the shelves we used to buy it at Walmart of all places by the quart and by the gallon; it can still be bought but it has to be ordered by mail it is even hard to find info in the Mobil 1 website but it is there it is one of the Porsche guys favorites it is even approved by Porsche. If I had to go back I'll use 15W50 because of the ZDDP that was lowered in the 5W50. The oil consumption compared with the times when the valve seals were worn with the M1 is about the same perhaps it was a bit lower then but it also was 70K miles ago, nothing to be concerned then or now.
Thanks!
George

 

[freezing1]

Two questions:

Is this a 3.0 l V-6?

and

if so, has it had the heads rebuilt at any point in its life?

 

[mene]

Originally Posted By: freezing1
Two questions:

Is this a 3.0 l V-6?

and

if so, has it had the heads rebuilt at any point in its life?

No it is the OVHC 2.6L straight 4, and the head was taken out to fix a porosity leak but everything else was untouched, valve seals replaced yes and timing chain too, that's all.
George.

 

[Ken2]

Generally speaking, you need to match the oil's viscosity with the oil gap (clearance) in the bearings. If there isn't much bearing wear, then there isn't much need to increase the viscosity. The oil pressure is a good indicator. More wear will result in more loss of oil out of the bearings, and higher viscosity oil partly makes up for that.

As the experience has shown, our engines are highly tolerant of different oils. That engine runs well with a 50 wt and with a 30 wt.

What was said about HTHS viscosity? That is the best measure of the oil's protection against wear in the engine. High HTHS vis has the one drawback of slightly increasing drag and the resulting minor loss of fuel economy.

I don't understand all the misunderstanding about the oil pressure and flow inside the engine. It is simple (and assuming everything is at normal operating temperature). The oil pump puts out a rate of flow proportional to its speed. The oil pump has a pressure regulating valve that dumps some output back to the sump to give about constant output pressure when the engine is up to speed. The oil filter has its internal differential pressure bypass, but this effects the oil flow to the engine very little. Beyond this the oil pressure is mainly effected by the size of the clearances for the oil to spill out of. The whole thing about oil flow rates is NOT a big deal. That Haas guy who wrote about it is a cosmetic plastic surgeon, not an engineer. You just need enough flow of oil into the bearings to have sufficient oil present for the bearing to create its hydrodynamic wedge of oil, and that can develop a pressure of hundreds of psi inside the bearings. As hot oil spills out, new cool oil is pumped in, and the engine keeps running and running and running and running....

 

[45ACP]

Originally Posted By: mene
So, the consensus seems to be "not" to raise viscosity until pressure drops to the limit and I'm perfectly OK with that. Now what about going beyond that and lower viscosity even more and go under the manufacturer recommendations? What do you think? Catherham? It does have 440K miles but it runs great. Maybe lowering one "click" at a time, but How much will be noticeable? 0.5 HTHS cst will do it or is it too much?
George.


You can do that, yes.

 

[Garak]

Originally Posted By: mene
My worries are that I don't know is wear occurs exponentially or linear, I'm not sure that the body will last another 400K; besides at the rate we are improving with oils maybe in another 10 years wear will be 0.


Well, I don't know what the graph of wear versus time would look like, but I have a suspicion it's not linear; or, at least if it's linear, it gets to a point where something critical happens. Nonetheless, I agree that the body will probably not be in the best of shape. Engines tend to outlast bodies. In any case, you've done very well with this vehicle.

As for going thinner, see what CATERHAM recommends. Personally, I'm a little gunshy about going thinner than recommended, particularly in such a dated vehicle (yes, my F-150 is the same vintage). I'm also gunshy of going thicker than recommended, for that matter.

 

[TFB1]

If it now running 5-10 psi less than original, I'd move up a 5W-40 to see if normal pressure can be restored... A 5W-40 surely isn't going to cause any problem, especially in FL...

 

[45ACP]

Originally Posted By: TFB1
If it now running 5-10 psi less than original, I'd move up a 5W-40 to see if normal pressure can be restored... A 5W-40 surely isn't going to cause any problem, especially in FL...


Oh come on! You know you NEED to use a 0W-20, especially in FL.

 

[mene]

Originally Posted By: Ken2
Generally speaking, you need to match the oil's viscosity with the oil gap (clearance) in the bearings. If there isn't much bearing wear, then there isn't much need to increase the viscosity. The oil pressure is a good indicator. More wear will result in more loss of oil out of the bearings, and higher viscosity oil partly makes up for that.

As the experience has shown, our engines are highly tolerant of different oils. That engine runs well with a 50 wt and with a 30 wt.

What was said about HTHS viscosity? That is the best measure of the oil's protection against wear in the engine. High HTHS vis has the one drawback of slightly increasing drag and the resulting minor loss of fuel economy.

I don't understand all the misunderstanding about the oil pressure and flow inside the engine. It is simple (and assuming everything is at normal operating temperature). The oil pump puts out a rate of flow proportional to its speed. The oil pump has a pressure regulating valve that dumps some output back to the sump to give about constant output pressure when the engine is up to speed. The oil filter has its internal differential pressure bypass, but this effects the oil flow to the engine very little. Beyond this the oil pressure is mainly effected by the size of the clearances for the oil to spill out of. The whole thing about oil flow rates is NOT a big deal. That Haas guy who wrote about it is a cosmetic plastic surgeon, not an engineer. You just need enough flow of oil into the bearings to have sufficient oil present for the bearing to create its hydrodynamic wedge of oil, and that can develop a pressure of hundreds of psi inside the bearings. As hot oil spills out, new cool oil is pumped in, and the engine keeps running and running and running and running....


Hi Ken, you see that is what keeps me wondering, my conundrum and the reason for the question in the first place, after reading a lot in the forum I'm only partially convinced and that is why I stopped at the lowest viscosity recommended by Chrysler instead of going lower since the oil pressure in theory allows it. Your opinion and JAG's comment about positive displacement, higher flow and higher pressure with a thicker oil is what my side of the brain in favor of thicker oil keeps telling me; yes, the engine is more lively now with the thinner oil, yes there are no noises to be concerned either (but it is noisier) and I haven't noticed any increase in MPG neither, but that is not important to me since it will be minuscule, what is important to me is longevity. I have also noticed contrary to common understanding is that it takes a little longer for the oil to reach the valvetrain with the thinner oil. Thanks!
George.

 

[mene]

Originally Posted By: TFB1
If it now running 5-10 psi less than original, I'd move up a 5W-40 to see if normal pressure can be restored... A 5W-40 surely isn't going to cause any problem, especially in FL...

Hi TFB1, To bring oil pressure back to "as new" I will have to use 50 straight, Back when we bought it with 140K the pressure with M1 5W50 (4.4 HTHS vis) it was 20 psi bellow bypass hot and at idle, at bypass at 900 rpm, and we could have used 20w50 since it is one of the viscosities recommended.

 

[mene]

Originally Posted By: 45ACP
Originally Posted By: TFB1
If it now running 5-10 psi less than original, I'd move up a 5W-40 to see if normal pressure can be restored... A 5W-40 surely isn't going to cause any problem, especially in FL...


Oh come on! You know you NEED to use a 0W-20, especially in FL.

Hey 45ACP, synthetic 0w20 with 1200ppm Phos. is hard to come by, but I was looking at a Crisco bottle in the supermarket and wondering.....

 

[mene]

Glad I'm not alone with my doubts.

 

[45ACP]

Originally Posted By: mene
Glad I'm not alone with my doubts.


Believe it or not, Redline 0W-20 is actually the lightest 0W-30 you can get.

I actually look forward to using it in a car one day.

btw: Royal Purple and Redline are high in that too, i think. Phosphorous = Zinc/ZDDP right?

 

[mene]

IIRC redline 5w20 have a HTHS of 2.8cst almost in the 30w area.
but again i'm hesitant to go that low now, maybe after a couple of OCI's with the ACD (3.4vis HTHS) I might sum up the courage and go with the redline.

 

[45ACP]

Originally Posted By: mene
IIRC redline 5w20 have a HTHS of 2.8cst almost in the 30w area.
but again i'm hesitant to go that low now, maybe after a couple of OCI's with the ACD (3.4vis HTHS) I might sum up the courage and go with the redline.


Redline seems a good choice for you and its near impossible to go thicker than their 5W-50 oil.

As a matter of fact.. maybe you should use that one. HTHS 5.9!!!!!!

 

[TFB1]

Originally Posted By: mene
Originally Posted By: TFB1
If it now running 5-10 psi less than original, I'd move up a 5W-40 to see if normal pressure can be restored... A 5W-40 surely isn't going to cause any problem, especially in FL...

Hi TFB1, To bring oil pressure back to "as new" I will have to use 50 straight, Back when we bought it with 140K the pressure with M1 5W50 (4.4 HTHS vis) it was 20 psi bellow bypass hot and at idle, at bypass at 900 rpm, and we could have used 20w50 since it is one of the viscosities recommended.


OMG if you want to believe all the tails(yes that's the correct spelling)here on BITOG, you've no doubt wiped out the bearings LOOOOONG ago...

 

[jorton]

Thick oil testimonial. I now know of 2 persons who know thicker oil does not cause rapid excessive wear. The other fellow has either changed grades to 30, or moved on.

mene I know not many keep the same vehicle to 440k(miles not kilometers) but no one has replied you used oil that's too thick. There are some members contemplating therapy now!

 

[mene]

Originally Posted By: 45ACP
Originally Posted By: mene
IIRC redline 5w20 have a HTHS of 2.8cst almost in the 30w area.
but again i'm hesitant to go that low now, maybe after a couple of OCI's with the ACD (3.4vis HTHS) I might sum up the courage and go with the redline.


Redline seems a good choice for you and its near impossible to go thicker than their 5W-50 oil.

As a matter of fact.. maybe you should use that one. HTHS 5.9!!!!!!

Well if you believe Brad Penn's website their 20W50 is 6+

 

[mene]

Originally Posted By: TFB1
Originally Posted By: mene
Originally Posted By: TFB1
If it now running 5-10 psi less than original, I'd move up a 5W-40 to see if normal pressure can be restored... A 5W-40 surely isn't going to cause any problem, especially in FL...

Hi TFB1, To bring oil pressure back to "as new" I will have to use 50 straight, Back when we bought it with 140K the pressure with M1 5W50 (4.4 HTHS vis) it was 20 psi bellow bypass hot and at idle, at bypass at 900 rpm, and we could have used 20w50 since it is one of the viscosities recommended.


OMG if you want to believe all the tails(yes that's the correct spelling)here on BITOG, you've no doubt wiped out the bearings LOOOOONG ago...

No, TFB1 I'm trying to see in the fog, I will have no problem going back to thick oil or even thicker oil if will serve my needs, if M1 5W50 was too thick the engine would have been dead long ago; you see, I use the car for our business and I start it run it for 10 miles perhaps and shut it down, then restart it 15~20 minutes later drive 3~4 miles and stop again and this goes on and on three days a week sometimes more so, the oil do reach operating temp. but then it cools down, warms up, cool down, and so on. My interest in the thinner oil is of course overall protection specially in all those dry starts and it's supposedly quicker flow to the parts. I couldn't care less for acceleration, it is nice but not a priority neither is the 0.25 MPG improvement if it does exist at all, my objective is longest engine life and less OCI if at all possible.
George.

 

[mene]

Originally Posted By: jorton
Thick oil testimonial. I now know of 2 persons who know thicker oil does not cause rapid excessive wear. The other fellow has either changed grades to 30, or moved on.

mene I know not many keep the same vehicle to 440k(miles not kilometers) but no one has replied you used oil that's too thick. There are some members contemplating therapy now!


Hi Jorton, The Factory Service Manual (the one to do repairs) spec's for our climate 10W40/30/20W50 and if I consider some lower temperatures then the 10W30 too; so the M1 5W50 couldn't possibly be too thick unless somebody knows something Mitsubishi doesn't or the viscosity grade values have changed since 1983 and now are thicker with the same number. More over if you check the HTHS vis of M1-5W50 is about the same as a good 40 so it will be around the middle of the range for the temperatures in our area.
George.