When to go up in viscosity because of wear?

[mene]

Hello, This is my second time asking for advice, have been lurking in the forum and the website for almost a year and have found almost all my answer but a few, I already posted another in the maintenance section and I think this one goes here, I hope I'm right and sorry if I'm wrong. To the point. When should I increase viscosity due to wear? should I go by Mileage?, Age?, Oil pressure?, Roll the dice?, Wheel of Fortune? None of the above?, All of the above?. I have read the motor oil university the engine is very clean, I have run M1 5w50 for the last 300K, oil pressure has gone down gradually over time/millage it burns about 1qt./2500 miles, from experience most of it is through the valve seals and I'll be changing them during the year, right now the engine is using Amsoil ACD (10W30,30) which in turn is the lowest viscosity recommended by the FSM and the pressure is well above the minimum, it runs good, no new noises and is more lively most likely because of less windage and parasitic losses but my main interest is longevity, I'll go back to a heavier oil if it will make it last the most. Your opinion will be greatly appreciated!
George.

 

[oggb]

My guess: engine will die of something not at all oil related.

 

[dparm]

Thicker oil does not necessarily prevent wear, it just puts a band-aid on a bigger problem.

 

[fxrider]

I think its time for a DINO high Milage oil ?? Castrol HM 10W30 ...

 

[mene]

Originally Posted By: JRed
My guess: engine will die of something not at all oil related.

Probably, but most likely the whole chunk of steel around it will finally disolve due to corrosion.

 

[mene]

Originally Posted By: dparm
Thicker oil does not necessarily prevent wear, it just puts a band-aid on a bigger problem.
.

That is my conundrum, I have heard all my life that thicker is better for longevity, and now the table seems to have been turned, that is why it now has 10w30 and I'm happy so far, but...

 

[mene]

Originally Posted By: fxrider
I think its time for a DINO high Milage oil ?? Castrol HM 10W30 ...


Not to be rude at all, but What does Dino vs. Synthetic has anything to do with the viscosity? and by the way I tried M1 10w40 HM and the engine hated it all the way to the OCI @ 5K miles, plus the synthetic is more shear stable under load and in the long run so it should protect better at the same HTHS cst, Right?, and I do use dino in other applications so I have nothing against it.

 

[CATERHAM]

Originally Posted By: mene
When should I increase viscosity due to wear? should I go by Mileage?, Age?, Oil pressure?, right now the engine is using Amsoil ACD (10W30,30) which in turn is the lowest viscosity recommended by the FSM and the pressure is well above the minimum, it runs good, no new noises and is more lively

Welcome to BITOG George.

Yes the answer is oil pressure or more specifically the oil back pressure that you read on an OP gauge. That's the best proxy for knowing the operational viscosity in a running engine.
Since your OP is well above the minimum with the 30wt oil your running you'll likely never need to run a heavier oil.
There are a lot of factors that contribute to engine wear, but as far as an oil's viscosity is concerned running the lightest oil that still provides the optimum minimum OP when the oil is as hot as it ever gets is the best approach.
A diesel oil is not necessary and a higher viscosity index 5W-30 oil is preferred over a 10W-30 even in the summer months.

 

[Garak]

I'd say keep an eye on your pressure. You say it's dropping, but still well within specifications of the FSM. If it's still well within specs, keep doing what you're doing. A multigrade 30 weight oil should be more than sufficient, at least for the time being.

The bandaid comments are right, too. If pressure drops below the FSM limits where you have to increase viscosity, obviously, the engine will eventually need some work, but the thicker oil will keep it running in the interim. Same goes for leaks being addressed with high mileage oil.

Considering the mileage you've accumulated on the Caravan, no one can accuse you of shoddy oil change practices.

My fleet usage of vehicles of that era involved only 10w-30 conventional oil, achieving up to 1,000,000 km before retirement from service.

Any vehicle that has done over 400,000 miles doesn't owe you a thing.

 

[mene]

Originally Posted By: CATERHAM
Originally Posted By: mene
When should I increase viscosity due to wear? should I go by Mileage?, Age?, Oil pressure?, right now the engine is using Amsoil ACD (10W30,30) which in turn is the lowest viscosity recommended by the FSM and the pressure is well above the minimum, it runs good, no new noises and is more lively

Welcome to BITOG George.

Yes the answer is oil pressure or more specifically the oil back pressure that you read on an OP gauge. That's the best proxy for knowing the operational viscosity in a running engine.
Since your OP is well above the minimum with the 30wt oil your running you'll likely never need to run a heavier oil.
There are a lot of factors that contribute to engine wear, but as far as an oil's viscosity is concerned running the lightest oil that still provides the optimum minimum OP when the oil is as hot as it ever gets is the best approach.
A diesel oil is not necessary and a higher viscosity index 5W-30 oil is preferred over a 10W-30 even in the summer months.

Catherhan I never thought you would look at this thread, I can count myself lucky. OK, the reason why I choose ACD is because was the one I found at the time with the lowest HTHS cst (you see I have read your stuff) with the right amount of ZDDP, with a good package to keep the seals fresh since it doesn't leak but the valve seals. Now I have looked at Redline 0W30 or 5w20 and I think one of those is next.
George.

 

[Astro14]

Oil pressure is the determinant in when you (might) have to increase...I have been running the highest OM recommended viscosity in the summer (10W40...OK, actually, 5W40...same thing...) and in the winter, a 10W30 (also the standard recommendation). With 229,000 miles on the truck, OP is well within limits, no crazy viscosity needed.

Plan on running 10W30 through the OCI, including summer...and will watch the OP gauge at idle...but I suspect it will be fine...

 

[mene]

I'd say keep an eye on your pressure. You say it's dropping, but still well within specifications of the FSM. If it's still well within specs, keep doing what you're doing. A multigrade 30 weight oil should be more than sufficient, at least for the time being.

The bandaid comments are right, too. If pressure drops below the FSM limits where you have to increase viscosity, obviously, the engine will eventually need some work, but the thicker oil will keep it running in the interim. Same goes for leaks being addressed with high mileage oil.

Considering the mileage you've accumulated on the Caravan, no one can accuse you of shoddy oil change practices.

My fleet usage of vehicles of that era involved only 10w-30 conventional oil, achieving up to 1,000,000 km before retirement from service.

Any vehicle that has done over 400,000 miles doesn't owe you a thing.

[/quote
I agree, the car doesn't owe me anything, and the oil pressure drop has been over 15 years or more, the engine is working fine, no leaks, only in the valves, everything begun when I couldn't find M1 5W50 in the shelves and started to investigate, one thing led to another, the LM engineering paper, then Widman's papers, then Bitog and here I am now looking for less viscosity since the work the car endures every week is beyond severe service, well beyond it most like torture. And Thanks!
George

 

[mene]

By the way Thanks for the warm welcome.
George.

 

[mene]

Originally Posted By: Astro14
Oil pressure is the determinant in when you (might) have to increase...I have been running the highest OM recommended viscosity in the summer (10W40...OK, actually, 5W40...same thing...) and in the winter, a 10W30 (also the standard recommendation). With 229,000 miles on the truck, OP is well within limits, no crazy viscosity needed.

Plan on running 10W30 through the OCI, including summer...and will watch the OP gauge at idle...but I suspect it will be fine...

WOW the heavy hitters, Catherham, Garak, Astro14! Yes I'm planning on running it in the summer which are usually brutal here with days in the 100's. From my experience t he pressure will drop but not enough to reach the limit, I still have more ACD to use since it is sold by the gallon. Thanks to all!
George

 

[Garak]

Yep, mene, sounds like normal wear, with respect to oil pressure loss. It certainly doesn't sound critical. Considering the mileage, it wouldn't even be "normal" wear, I venture to say. Very slow might be a better adjective.

I know the siren song of thick oil. It must be congenital, rather than genetic, though, since my dad was a thin oil advocate (and into 30 weights) when everyone else was using 10w-40 or straight grades.

In another 400,000 or so miles, when the oil pressure drops to critical, switch to a 15w-40 or 20w-50 conventional while you shop for a new vehicle. It'll hold everything together between test drives.

 

[Warstud]

Pressure doesn't = flow
Thicker oil increases pressure....decreases flow
Rebuilt engine increases pressure

 

[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.
George.

 

[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.

 

[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.

 

[Loobed]

Originally Posted By: mene
When should I increase viscosity due to wear? should I go by Mileage?, Age?, Oil pressure?, Roll the dice?, Wheel of Fortune? None of the above?, All of the above?.
George.


opinion - oil pressure, or when you feel like it.