Mobil 15w50 in 0w20 engine.

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Originally Posted By: Gokhan
Originally Posted By: Vlad_the_Russian
- Really enjoying the smoothness of throttle response in the lower RPM range. Feels like the engine gained some torque. Can't explain why... Better ring seal?... BUT hate the slight HP loss in the upper RPM range. Very minor, but the loss is there.

According to the fundamental curve of lubrication -- Stribeck curve -- minimum oil-film thickness (MOFT) and friction increase with viscosity (n [eta]) and RPM (v) and decrease with engine load (P) in the hydrodynamic region. Therefore, it makes sense that you see more effect at high RPM than at low RPM. However, I don't know how you control RPM for a given engine load if you don't have a manual transmission.

It makes little or no sense that the engine gained HP at low RPM with thicker oil. The only way that would happen is that your engine is running in the boundary region -- metal-to-metal contact -- and about to fail. I take the more plausible explanation that it's merely a subjective, psychological observation.

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Your MPG didn't change going to a thicker oil? Given how impossibly difficult it is to measure MPG, no one here would believe that.

Toyota engines can tolerate pretty much any viscosity. However, as most people here said, you will gain no benefit from running such an unnecessarily thick oil. Your oil temperature and pressure will be unnecessarily high. You will lose HP and MPG regardless of RPM. Wear-protection benefits? You will be lucky if thicker oil actually doesn't end up producing more wear. Simply run the recommended oil for the most HP, MPG, and probably the longevity as well.

Someone here posted that all engines with a carburetor must run 20W-50. I laugh at such old wives' tales posted on the Internet. I run 0W-20 in a 1985 engine with a carburetor with no problems. Fuel dilution? I've never experienced it.

Here we go again
 
Originally Posted By: SR5
Originally Posted By: Gokhan
You will be lucky if thicker oil actually doesn't end up producing more wear.

..........

I laugh at such old wives' tales posted on the Internet.

.........

I run 0W-20 in a 1985 engine with a carburetor

So you say a thicker oil can produce more wear, based on what ? It needs to be better than two simple UOAs from your 1985 Toyota 4-cylinder.

Sounds like you are trying to start a few new wives' tales of your own.


If a single UOA is enough to prove a point, here's one that I posted from an Oz car forum member that asked me to post it...
https://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2446765

3.8 V-6 tuned to get 200KW, serious mileage on the dial, and 15W50 M1 rather than the ILSAC 5W30 that the engine would get in the states...not bad, eh ???

Although I would invite Gokhan to point to the indicators of excess wear that are "likely" in such an event...
 
Originally Posted By: TheKracken
I run 0w20 in my mini van that calls for 5w30 and I have noticed nothing but good. So much smoother and the throttle response is somehow much better. I have not preformed any UOA comparisons but I am so far a believer.

Next I will be switching my truck that calls for 10w30 to a good 0w20 and hope for similar results.


OK then.


Why?
 
Originally Posted By: SR5
Originally Posted By: Gokhan
You will be lucky if thicker oil actually doesn't end up producing more wear.

..........

I laugh at such old wives' tales posted on the Internet.

.........

I run 0W-20 in a 1985 engine with a carburetor

So you say a thicker oil can produce more wear, based on what ? It needs to be better than two simple UOAs from your 1985 Toyota 4-cylinder.

Sounds like you are trying to start a few new wives' tales of your own.

Laws of Physics (with repeatability) proves otherwise.
 
I like when those quote Laws of Physics yet are not willing to go any further on how that is any proof... My minor was in physics and the few arguments put forth don't seem to really make any sense other than to the layman who doesn't know physics all that well. I would argue that the flow argument put forth by the thin oil guys on this forum makes more sense. Thick oil I would agree might have a higher safety margin to work with if your car overheated or ran out of most of its oil...but in a normal working and operating vehicle being used in normal and some severe service could benefit from thinner oils. That is just what I can make out from the arguments and since I am not an engineer I will not try to convince anyone differently.
 
Originally Posted By: TheKracken
I would argue that the flow argument put forth by the thin oil guys on this forum makes more sense.


They keep talking "flow", but then refuse to engage the part where the flow is dictated by the "positive displacement pump" that can only ever "flow" a certain number of millileters per engine RPM...

Except at the limits of pumpability, and the "W" rating comes in....but that's an inconvenient truth

Note, "flow" doesn't lubricate.

And when the oil is within it's pumpable range (i.e. it's well above the limits of it's "W" rating), it fills the galleries, and gets to the remote ends at pretty well exactly the same time.
 
Originally Posted By: TheKracken
Thick oil I would agree might have a higher safety margin to work with if your car overheated or ran out of most of its oil...but in a normal working and operating vehicle being used in normal and some severe service could benefit from thinner oils.


Note on that point, Ford and Subaru, in their "high performance" cars have systems that cut the power output in response to high oil tmperatures on their 20 grade "performance cars"...those cars, when operated ENTIRELY within their design performance envelope, albeit at the top end of their envelope "outrun their oil", and have to be protected by it.

No, it's not the same as the ford Oz system that will limp you home with a failed cooling system, it's operation entirely within their design operating margin.
 
Originally Posted By: Shannow
Originally Posted By: TheKracken
I would argue that the flow argument put forth by the thin oil guys on this forum makes more sense.


They keep talking "flow", but then refuse to engage the part where the flow is dictated by the "positive displacement pump" that can only ever "flow" a certain number of millileters per engine RPM...

Except at the limits of pumpability, and the "W" rating comes in....but that's an inconvenient truth

Note, "flow" doesn't lubricate.

And when the oil is within it's pumpable range (i.e. it's well above the limits of it's "W" rating), it fills the galleries, and gets to the remote ends at pretty well exactly the same time.


Looked up positive displacement pump and it is starting to make more sense (assuming most vehicles use this sort of pump?)

How about the argument that a thinner oil will be closer to desired operational viscosity before a thicker oil will. It will at full operating temperature be thinner than the desired visc. but since the majority of wear is said to happen at start up and warm up this might mean that a thin oil will produce less wear than a thicker oil might. Then once you are at proper oil temp we have to see more about if a thin oil is enough to protect your engine within the designed operational temperature. Obviously exceeding this is going to thin out your oil and that safety margin will close pretty quickly.
 
Originally Posted By: TheKracken
I would argue that the flow argument put forth by the thin oil guys on this forum makes more sense.

Shannow has a chart somewhere from a paper demonstrating that at any reasonable temperatures (i.e. where CCS and MRV aren't being challenged), the difference in flow between very different viscosities is inconsequential. With a positive displacement oil pump, it really doesn't matter, as long as you're able to pump the oil. Now, if it's -40 and you're trying to compare a monograde SAE 30 versus a 0w-20, there will be obvious differences, like the Esso video that gets shown regularly here. If it's 10 C, you won't see a difference.
 
Originally Posted By: TheKracken
I would argue that the flow argument put forth by the thin oil guys on this forum makes more sense.
That is just what I can make out from the arguments and since I am not an engineer I will not try to convince anyone differently.


But that is the problem - you have some people on the forum who are convinced of how something works based simply on what 'makes more sense', and there are others on the forum who have formal training in particular fields of science and have an understanding of how things actually work. Just because something 'makes sense' or seems to be 'common sense' or 'intuitive', doesn't mean that it is correct.

Lubrication doesn't require flow. If it did, the little sleeve bearing in the fan cooling the CPU of your computer would have seized the first time it spun. The bearing doesn't have an oil pump feeding it so there is no oil flow to speak of, only a small fixed quantity of lubricant, yet it is clearly being lubricated.
 
Originally Posted By: TheKracken


How about the argument that a thinner oil will be closer to desired operational viscosity before a thicker oil will. It will at full operating temperature be thinner than the desired visc. but since the majority of wear is said to happen at start up and warm up this might mean that a thin oil will produce less wear than a thicker oil might. Then once you are at proper oil temp we have to see more about if a thin oil is enough to protect your engine within the designed operational temperature. Obviously exceeding this is going to thin out your oil and that safety margin will close pretty quickly.


These thin oils were initially made for hybrid engines where the gas motor would constantly start and stop never reaching full operating temperature.
 
Originally Posted By: Virtus_Probi
Originally Posted By: SR5
And this UOA produced only 1 ppm iron on GTX 20W50

https://bobistheoilguy.com/forums/ubbthreads.php/topics/4325388/

It's a thick oil And a mineral oil ....... Oh the humanity !!


All the wear iron got stuck in the sludge that dino was turning into!!
;^)

Yes, but run it out to 10,000 miles and it will start laying down that sludge metal on your bearings, tightening up that old engine nicely, here your BlackStone UOA should start returning negative numbers.
 
Last edited:
Originally Posted By: igs
These thin oils were initially made for hybrid engines where the gas motor would constantly start and stop never reaching full operating temperature.


No they weren't
 
All of this comes down to bearing clearances (gap) and the oil film thickness that is needed to fill that gap.

The start-up wear often stated on BITOG is usually related to the cylinder walls in the ring belt area. It is mostly due to condensation, water vapor, and unburnt fuel washing the oil off the cylinder walls just after start-up ...

The only cure (band aid) for this is retained oil film from when the motor was shut off. That is mostly a function of viscosity and surface tension which are usually better in dino oils, and thicker is better ... Thin oils leave precious little retained film on the cylinder walls.

But, the blocks and liners have been getting harder (more nickle) and the rings have been getting better, so there MAY be less need for retained film thickness ... And EFI cars have better control over the fuel atomization and distribution, so fuel wash is less of a problem. These advances allow thinner oils with approximately the same wear rates. However, if you step up a range in viscosity and have some dino oil in the mix, it is my "belief" that the wear numbers will drop.

If your new fav oil needs a ton of VII's to get your range, all bets are off. But 0W-20 with a can or two of SAE 30 might keep that motor alive a few years longer. For rust belt folks, it means nothing. For those of us who regularly buy/drive 20~25 year old cars and trucks, it means a lot
smile.gif
 
Originally Posted By: Shannow
Originally Posted By: igs
These thin oils were initially made for hybrid engines where the gas motor would constantly start and stop never reaching full operating temperature.


No they weren't


Honda Insight
 
Originally Posted By: TheKracken
I like when those quote Laws of Physics yet are not willing to go any further on how that is any proof... My minor was in physics and the few arguments put forth don't seem to really make any sense other than to the layman who doesn't know physics all that well.


http://www.machinerylubrication.com/Read/1318/tribology-lubricant-selection

1)Increase in operating viscosity leads to increase in EHL oil film thickness;

2)Increase in EHL oil film thickness leads to increase in specific oil film thickness;

3)Increase in specific oil film thickness shifts lubrication regimes :

a)From Boundary Lubrication to Mixed Lubrication (and possibly Elasto Hydrodynamic Lubrication, or lighter end of BL) regimes ;

b)From Mixed Lubrication to EHL lubrication (and possibly Hydrodynamic Lubrication, or lighter end of ML) regimes;and

c)From EHL lubrication to Hydrodynamic Lubrication (and/or more viscous end of EHL) regimes .
 
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