When to go up in viscosity because of wear?

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Stick with what works...go back to using the M1-5W50. With 440K miles on it you must be doing something right. Drive it till it quits.
 
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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.
JAG, I don't know what point you're trying to make here. Thick oil flows through an engine slower than thin oil; period.
 
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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.
In running Amsoil ACD 10W-30 with it's HTHSV of 3.4cP and low 141 VI you're already running an oil heavier than specified. A typical PCMO 5W-30 has a HTHSV of 3.1cP and and syn' oils of that grade a 170 VI. So if you ran some 5W-30 you will notice a drop in oil pressure particularly on start-up but it will still be higher than the spec' minimum. Honestly, with the mileage you have on that engine (does the vehicle have any market value?) I wouldn't be running any expensive oil; what's the point? At most I'd suggest any syn' 5W-30 you can get on sale or even a 5W-30 dino.
 

mene

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Hi CATHERHAM, Well, It is our goal to run it for another 30~40K miles, that will be 2 years and in that time we will be making drastic changes to our lives, and the van will go either way. Regarding synthetic or dino I'm trying not to accelerate wear, not to create leaks and not increase the frequency of OC. Also in another post I mentioned that the work the van does is an "engine start and engine off" every 20 to 40 minutes and driven 3~5 miles in between, the oil do get to temperature but cools about 40F average in those off minutes and it happens around 20 times/day for 3 days every week plus regular errands, so that high VI from synth comes in handy since I want the oil to reach all the engine as soon as possible. As you noted the car doesn't have any market value, it is the first of it's type but doesn't have any collecting value either at least at this point. I do get the ACD for little over $7.00 and we have a distributor in the city so no extra for shipping and last time I checked M1 in Wallyworld it was almost $7 for 0w40 and still short on ZDDP, the 15W50 is available only at parts stores for about $12; all the other inexpensive synth's are way low in ZDDP. But I'm open to suggestions so please don't hesitate and post them, to all of you guys. Thanks! George
 

JAG

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Originally Posted By: CATERHAM
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.
JAG, I don't know what point you're trying to make here. Thick oil flows through an engine slower than thin oil; period.
I'm trying to make the point that is in disagreement with what you said, provided that the assumptions I stated are used. I'm all ears for your explanation.
 

mene

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Originally Posted By: 45ACP
Supertech 10W-40 and be done with it lol. Save money. Live better.
It is tempting but I'll be changing oil every 8 to 9 weeks, I might just replace the drain plug with a cork and leave the filter tool in the floor indefinitely.
 
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Yeah on older motors that are nearing rebuild time, with hogged out main bearings 20w50, or 15w40 can help you keep oil pressure for a bit longer. Done it on plenty of beaters.
 
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Originally Posted By: JAG
Originally Posted By: CATERHAM
JAG, I don't know what point you're trying to make here. Thick oil flows through an engine slower than thin oil; period.
I'm trying to make the point that is in disagreement with what you said, provided that the assumptions I stated are used. I'm all ears for your explanation.
JAG, Its hard to get through to CATERHAM that use of oil OTHER THAN 0W-20 is also ok. Its sort of like this horse OP (mene) the post before this said this:
Quote:
Yeah on older motors that are nearing rebuild time, with hogged out main bearings 20w50, or 15w40 can help you keep oil pressure for a bit longer. Done it on plenty of beaters.
And that is ok. Use a 20W-50 dine, use whatever you want, use whatever you feel comfortable with. Your engine still has life. Use what you feel will lubricate its worm parts the best. Not someone else. thumbsup
 
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Originally Posted By: JAG
Originally Posted By: CATERHAM
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.
JAG, I don't know what point you're trying to make here. Thick oil flows through an engine slower than thin oil; period.
I'm trying to make the point that is in disagreement with what you said, provided that the assumptions I stated are used. I'm all ears for your explanation.
Basically it's your statement that "thicker oil will cause both higher oil pressure and higher flow rates". That's true but misleading. In an engine running at a fixed rpm, a lighter oil will result in higher oil flow with correspondingly lower oil back pressure. I'm sure you don't disagree with that?
 
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Originally Posted By: mene
I do get the ACD for little over $7.00 and we have a distributor in the city so no extra for shipping and last time I checked M1 in Wallyworld it was almost $7 for 0w40 and still short on ZDDP, the 15W50 is available only at parts stores for about $12; all the other inexpensive synth's are way low in ZDDP. But I'm open to suggestions so please don't hesitate and post them, to all of you guys.
Well, I wouldn't call the 50 weight "too thick" as a blanket statement. It certainly might be thicker than optimal, but that's neither here nor there. The engine has lasted forever and a day, and that's good enough for me. If you want something higher in ZDDP that isn't totally outrageous on price or difficult to obtain, you could consider something like QS Defy, other HM oils, or (if it were me) an HDEO in an appropriate grade. The latter are available in all kinds of grades, synthetic and conventional, and will have plenty of ZDDP. The other advantage is they are readily available in 5 gallon pails, which comes in handy for frequent oil changes. If you want cheap but more than adequate, any 15w-40 or 10w-30 HDEO will do. If you want to spend a bit more, there are plenty of synthetic HDEO options in 5w-40 and 0w-40. They will be plenty thick at operating temperatures, without being as thick as a 15w-40 or 20w-50 at startup.
 

JAG

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Quote:
Basically it's your statement that "thicker oil will cause both higher oil pressure and higher flow rates". That's true but misleading. In an engine running at a fixed rpm, a lighter oil will result in higher oil flow with correspondingly lower oil back pressure. I'm sure you don't disagree with that?
I do agree that it will have lower oil pressure. I think flow rate could be higher too although I could be wrong. I base my opinion on volumetric efficiency of gerorator pumps being higher as oil viscosity increases. See Figure 3 here: http://www.michael-smith-engineers.co.uk/pdfs/Metering%20Brochure.pdf If I'm wrong, it's probably because that type of efficiency curve does not apply to most automotive oil pumps or because of the effect of all of the different passageways that oil goes through in an engine. I actually better restrict my opinion to flow rate just after the pump but not through every oil passage because I don't believe it applies to flow through the holes in pistons. I don't care who is right...I just care that we get it right for the sake of knowledge.
 
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At the same temp, seems to me 30 psi of a 3.5 cSt oil would flow more quickly than 25 psi of 3.0, especially if the losses are due to clearances inside the pump...
 
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Thicker oil will cause a lower flow rate, that's the point. Low oil pressure is just to much flow. The mains are worn and letting to much oil past them. Quite a few old motors will idle at 0 PSI on hot days and be just fine for a long time..as long as they build enough pressure past idle. Low oil pressure starts to cause problems not because of flow their is plenty, but because of the lack of pressure to force oil where it needs to go. Using a real thick oil slows down the flow which increases pressure.
 

JAG

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Originally Posted By: TFB1
At the same temp, seems to me 30 psi of a 3.5 cSt oil would flow more quickly than 25 psi of 3.0, especially if the losses are due to clearances inside the pump...
That's what I think too.
 
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Originally Posted By: JAG
Originally Posted By: TFB1
At the same temp, seems to me 30 psi of a 3.5 cSt oil would flow more quickly than 25 psi of 3.0, especially if the losses are due to clearances inside the pump...
That's what I think too.
I don't agree because the psi figures you're likely referring to is not the oil pump pressure but a measure of oil flow resistance or the back pressure of flow through the engine bearings et al. Using your example, the 25 psi represents less resistance to oil flow because of the lighter 3.0cSt oil and therefore faster oil flow.
 

JAG

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Originally Posted By: CATERHAM
Originally Posted By: JAG
Originally Posted By: TFB1
At the same temp, seems to me 30 psi of a 3.5 cSt oil would flow more quickly than 25 psi of 3.0, especially if the losses are due to clearances inside the pump...
That's what I think too.
I don't agree because the psi figures you're likely referring to is not the oil pump pressure but a measure of oil flow resistance or the back pressure of flow through the engine bearings et al. Using your example, the 25 psi represents less resistance to oil flow because of the lighter 3.0cSt oil and therefore faster oil flow.
Let's forget the volumetric efficiency aspect for now. The principle behind a positive displacement pump is that for every revolution/cycle it pumps X amount of volume of fluid, regardless of viscosity.
 
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A positive displacement pump moves a certain volume of oil regardless of the "pressure". Increasing oil viscosity increases oil pressure at low speed, but it also DECREASES flow through the bearings at ALL speeds.
 
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I have a question related. I saw someone said not to mix oil with a 15 40 or 15-50 weight cause of a low vi (something like that) I would like opinions, can I mix 1/2 German Castrol 0-30(as they said it was thicker)with Mobil 1 HM 10-30 to still be using the called for 30 (opposed to moving up to a 40 wt) Thinking I am getting the add pack of the Mobil 1 High Milage + the thicker 30 wt of the German Castrol. Is this thinking OK or do those two not mix/ work well
 
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