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Discussion Starter #1 (Edited)
There have been many posts on which viscosity oil to use especially for the 5.7. I started thinking about this very thing after I modified my engine which included high pressure valve springs to support the cam I installed. So I thought between the higher pressure applied to the valve train due to the increased cam duration and stiffer valve springs and the additional horsepower going to the rod and main bearings I thought it was worth researching. After hours of research I have concluded that I’m good to run 0w-40 in my 5.7. I thought it would be good to post my results for those that are interested

The results I have are the following:
• Much quieter engine, I could hear the tick from the rockers clearly through my 1/78 headers which is now basically eliminated
• I monitored the oil pressure while running the 5w-20 to compare to the 0w-40. There is an average of 1-3lbs increase in the oil pressure using the 0w-40; the 3lb increase is more so when the oil is cold. No difference in pressure when warm at idle and cruising 1500-2100 rpm is still less than 3lb variation at higher RPMs. Which means the oil flow should not be restricted.
• No impact to gas mileage
• I assume no impact to HP, if so it’s not noticeable
• Oil temp the same
Note: I use Amsoil … not all oils respond identically as they have different combinations of additives and differences in the base oil. To add to that it’s suggested to pick a brand and stick with it due to the additives varying between brands. The chemistry of the oil how it cleans, prevents corrosion, viscosity etc... is carefully formulated, mixing brands can throw all of that out of line affecting the efficiency of the oil.

There are quite a few things to consider when choosing oil viscosity such as how the engine will be used, heavy loads at low RPM, High RPMs light loading, combination of loading with low RPMs and high RPMs, Expected longevity of the engine and the temperature of the environment. Engine tolerances come up quite often in the posts on the forums. They are now starting to adjust the tolerances to use the lighter viscosity oils. however, even with the tighter tolerances as long as you don't go way out of the viscosity range specified, running a slightly higher viscosity oil won't hurt anything.
The main driver behind lower viscosity oils is fuel economy. They are even pushing for a 16 viscosity rated oil, (Pennzoil already produces it). Thinner oils may provide better fuel economy, more horsepower, and better cooling. If there will be a lot of shock to the engine Low RPM heavy loading or a lot of sprint driving a higher viscosity will be better suiting. If the car is a daily driver and driven easy the lighter viscosity is more than likely the better choice. Another example would be if the engine was built to run on a track with the expectation of a short engine life. They would set tight tolerances and run thin oil.

As for temperature not all oils have the same “w” viscosity even though they have the same “w” rating, for example a 5w-20 has a lower “w” viscosity than the 0w-40 even though it’s 5w vs. 0w. The “w” viscosity corresponds with the total viscosity rating. So if you are in a cold climate and the oil never gets hotter than 160-180 degrees and car is started in freezing temps the lighter viscosity is probably the better choice.

As it relates more to this forum the 5.7 hemi running the 5w-20 will be fine however, if you want a little more insurance and you drive your car more on the aggressive side the 5w-30 could be a better choice. There is the debate that using a higher viscosity affects the MDS and VVT. The ability for the oil to flow properly through those systems does have some affect, but again if you don't stray too far from the suggested viscosity they shouldn't be affected. Actually the MDS lifters and VVT is the same on both the 6.4 and 5.7. so I assume switching from 5w-20 to 0w-40 (Full Synthetic) or the 5w-30 will have no impact on those components. One of the main reasons I took readings on the oil pressure was to see if the flow was restricted to any extent. If I would have seen a big jump in oil pressure I would have switched back.

I have heard some of the 5.7’s will trigger a code when using higher viscosity but I assume that is something in the software and a way to push the CAFÉ standards using the 5w-20.

Please note I’m no expert but as often as this subject comes up I thought it would be good to share my results from switching viscosity and some general information with my opinions based on what I have researched.
 

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What 19johned53 said.

Let me add...

First the quieter engine. Every time I changed the oil in my previous cars the engine would quiet down. Fresh oil even up to temperature is just quieter oil. As the oil is used, gains miles, it gains contamination and this affects the oil's viscosity and one result is the engine just makes more noise.

I have not monitored oil pressure with 5w-20 vs. 0w-40 but I have monitored oil pressure with 0w-40 and 5w-50 (not a typo for 15w-50!) oil in my 996 Turbo.

Based on my observations there is no way to tell from the oil pressure, cold, warm or hot, which oil is in the engine. While I did notice some variation in hot idle oil pressure it was a false alarm. This was due simply to ambient temperature differences. Cool days the hot idle oil pressure was up a bit to around 2.0 bar. On hot days the hot idle oil pressure was down, under 2.0 bar not much probably around 1.7 bar.

Thicker oil can affect gas mileage even performance. I discussed oil with the owner of a air cooled 911, a 993 model. He told me he had switched from 0w-40 oil to 15w-50 oil. This owner chose to ignore the fact that Porsche does not approve the use of 15w-50 in any of its modern -- starting around 1985 I think and newer -- sports cars. He admitted gas mileage dropped and his track times increased.

This is more serious than at first it might appear. The decrease in mileage and the increase in lap times suggests increased friction from the heavier oil. This increase in friction adds heat and it adds heat to the oil at the worst possible time and place: In the main/rod bearings. A thicker oil then can actually cause the oil film in the bearing to run hotter than it would otherwise, which could result in the oil breaking down. Thus the thicker oil can cause the very problem it was selected to avoid.

As for which viscosity of oil to use, my info is what basically controls this is the bearing clearances. Tight clearances one should use a lighter viscosity of oil. If the engine is built with larger/looser clearances, a higher viscosity oil could be called for.

If high loads/high RPMs are anticipated what becomes critical to the oil's ability to deal with this is engine coolant temperature and engine oil temperature control. Playing with oils with difference viscosity indices might seem the way to go but as I touched upon above a thicker oil may make the situation worse, not better.

Temperature control becomes even more critical.

As for ambient temperature concerns the only info I have on this is from my Porsche experience. Porsche called for the use of 0w-40 oil in ambient temperatures of -25C (-17F).

Otherwise, one could choose to run a number of different oil: 0w-40, 5w-40, and even one approved 5w-50 oil.

I never encountered extreme cold but more than once encountered extreme heat: up to 118F. Sometimes I had 0w-40 oil in the engine, at other times 5w-50. There was never any indication of any oiling issues at the time nor after I had put tens of thousands of miles on both engines. The oil must have done its job or I would have known it.

There is some desire to lower engine oil viscosity for fuel economy. As I touched upon above at least one owner of a car admitted to me his engine used more fuel with a thicker oil in the engine.

A race engine builder that I used to live next door to showed me a competition engine block he had prepared for a customer -- he had it in his truck as the customer was coming by later to pick up the block -- and as an ex-journeyman machinist I had to feel the bore finish. It was smooth, almost mirror like. I was expecting a rather rough cross hatch hone finish. I asked the engine builder about this and he said the bores are finished this way so 0w oil can be used which reduces oil friction. This has the benefit of not heating the oil up as much which reduces the heat load the oil has to deal with.

A lower viscosity oil is not necessarily to be rejected simply because of its lower viscosity.

A daily driver even driven easy is not necessarily easier on the oil. Many is the time in using my Boxster to run around town the coolant temperature would get up to 212F to the point the radiator fans would come on. I'm sure the oil temperature was elevated as well.

More recently with my Hellcat and its oil temperature display around town driving taking it very easy can and does have the oil temperature quite warm, easily up to 212F and even hotter. I think the hottest I've seen is 230F.

A daily driver is not the car with which to skimp on oil.

Over the years of oil discussion I have stated the only authority on what oil to use in an engine is the maker of the engine. If one elects to ignore the engine maker's oil selection if he wants to use something different then he can use any criteria he wants to justify his choice of oils: Lower cost, more (or less) viscosity, pretty bottle, more additive of the week, whatever. All are equal and equally useless on which is the right/best oil to use.

I will add that whatever oil one uses he should avoid running the oil too long. How long depends upon many factors: Type of driving; driving conditions, like high heat, high humidity, extremely dusty, etc. (On this note some areas of the country are classified by some auto makers as being harsh duty areas and as a result the auto maker recommends more frequent oil/filter services.) For where I live and drive and how I drive I have found 5K miles to be the number of miles to run oil, if 317K miles on one engine and 161K miles on another engine -- both of which ran at the end as good as they did at the beginning -- is any indication.

But a car used for short trips and doesn't accumulate that many miles might need its oil changed at fewer miles, or once a year, or more often if the auto maker says.

OTOH, a car driven strictly on the highway might be ok with an oil change at higher miles. I know in the past I've changed the oil before heading out on a long road trip and after a week or two on the road have come back with 4K or more miles on the oil. At 5K miles I would then change the oil again and often the oil draining out would still be translucent even have some amber color to it. It was "clear" to me that the 5K miles of highway/freeway driving was not as bad on the oil as was my more normal usage which while it still included some highway/freeway miles included way more miles of surface street driving.

All I can offer is at least change the oil on the automaker's schedule, miles or time, and if one wants to change the oil more often, that's not a bad idea.

In the engine and engine oil partnership oil is the sacrificial item. One throws away oil that probably has some amount of service life left and replaces it with fresh oil to avoid throwing away an engine.
 

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Discussion Starter #4 (Edited)
Hi Rockster.... thank you for all of the input. I feel like we said a lot of the sames things but worded a little differently. There are so many details that need to be included to really provide what is required to get a solid post on this topic it's hard to keep it general and not miss some points required for clarification.
 

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A race engine builder that I used to live next door to showed me a competition engine block he had prepared for a customer -- he had it in his truck as the customer was coming by later to pick up the block -- and as an ex-journeyman machinist I had to feel the bore finish. It was smooth, almost mirror like. I was expecting a rather rough cross hatch hone finish. I asked the engine builder about this and he said the bores are finished this way so 0w oil can be used which reduces oil friction. This has the benefit of not heating the oil up as much which reduces the heat load the oil has to deal with.
That's unusual - the object of the cross-hatching is for oil to remain within the machining to provide more lubrication.

A mirror finish bore is typically referred to as "glaze" and during a overhaul (not full rebuild) it would generally be recommended to hone the bore to obtain the cross-hatch pattern and help reduce oil consumption.
 
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That's unusual - the object of the cross-hatching is for oil to remain within the machining to provide more lubrication.

A mirror finish bore is typically referred to as "glaze" and during a overhaul (not full rebuild) it would generally be recommended to hone the bore to obtain the cross-hatch pattern and help reduce oil consumption.
Generally a cast iron cylinder is finished with a rough cross hatch pattern to facilitate ring seating. The cross hatch lines want to cross in an X with the angle between the X legs about 90 degrees with the long axis of the cylinder splitting the X in two.

(The time I manually honed a block's cylinders -- the 318 engine out of my Dodge D200 pickup -- I used the coarsest set of honing stones and had to move the hone in and out at a pretty fast clip to get the proper hatch angle.)

The cross hatch finish is intended to "machine" the rings so they adapt to the cylinder bore very quickly. They generally do. The newly rebuilt engines I have been around at first start the rings seat in just a minute or two. The engine starts and runs kind of rough, ragged and the mechanic raises the RPMs to 2K or even higher. The first time I am thinking the rebuild is at fault as the engine should be running better.

A bit of the rough running is due to the assembly oil that is in the combustion chambers burning away and as this burns away the engine runs better, but still not as good as expected.

But in a minute or so the engine sound mellows out and the engine smooths out and runs a lot better. This is the rings seating. The tech continues to run the engine at high RPMs this to ensure the lifters/cam lobes receive sufficient lubrication as they "break in".

After this initial run in -- which I recall went on for over 15 minutes ( the exhaust manifolds were red with heat ) the engine is shut down and the oil is drained and replaced with fresh oil -- generally the oil the engine will use from this point on -- and the filter is replaced then the engine is ready for use on the street though break in is not yet complete.

The roughness in the cylinder has disappeared but one can still see the cross hatch pattern in the cylinder wall. This provides tiny voids in which oil remains to provide good ring/piston wall lubrication.

In the case of the racing block the cylinder finish is very smooth so a thinner oil can be used. I was told a 0w-5 (that's '5') racing oil was used. The thinner oil reduces friction. I don't know how the cylinder walls retain oil given this smooth surface. Perhaps the oil is carried with the piston via some surface finish on the piston walls? I suspect there is a considerable amount oil sprayed against the underside of the piston to help cool it but also to help provide oil to lubricate the cylinder walls/rings/piston and this ensures adequate lubrication of the cylinder/rings/piston interface.

As for what if any break in this cylinder finish requires I have no idea. Maybe the engine is run "dry" on compressed air, turned by an electric motor, to break in the rings. Or maybe the engine is just fired up and run a while. This was strictly a race engine used in some drag car class (pro stock?) and to some level oil consumption was not a concern. The goal is all about maximizing power and one way is to reduce friction and the oil film between the cylinder walls and the pistons/rings represents considerable friction source.
 

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Hi

It seems oil pressure is being mistaken for oil flow in this thread, a high oil pressure is no good if you have no flow.

Regards

Dereck
 

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Discussion Starter #8
Hi

It seems oil pressure is being mistaken for oil flow in this thread, a high oil pressure is no good if you have no flow.

Regards

Dereck
The entent of the post is to discuss the differences of how the engine will perform and be protected using different viscoty oils.

To your point here is a decent write up.

"How much oil pressure is enough? Keep in mind that what counts is flow. A time proven rule of thumb is 10psi/1,000rpm. This assumes the normal range of engine bearing clearances and it is well proven that 10psi/1,000rpm will supply enough oil flow when normal clearances and parts are used. Since we have no convenient way to measure flow, we use pressure as a surrogate. If the bearing clearances are larger, we need more flow to keep an adequate film of oil between the bearings and the shaft. Do we need more oil pressure? No, but it will take more volume to produce the same pressure because the resistance is lower. So, we need a high volume pump to maintain oil pressure. This costs hp – more power is needed to drive a HV pump."

What if the bearing clearances are tight? Well, we will see more pressure with the same output but we don’t need it. In that case, we can use a lower viscosity oil with less friction and less resistance to pumping. This will lower the oil pressure and gain hp because of the lower pumping losses and less friction. This is what the OEM’s are doing to improve mileage and performance. Some new vehicles come with a recommendation for 5W-20 oil. There are real hp gains from using a low viscosity oil. Some hard core racers will use 0W-10 weight. The problem is that there is a general relationship between viscosity and shear strength. Low viscosity oil may not provide enough resistance to shear to protect bearings (avoid metal to metal contact) under very high loads (high boost blower cars, heavy nitrous use, etc.).

Sent from my SM-T350 using Tapatalk
 

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Don't know about the Hellcat engine but the Porsche engine oil pump can flow around a liter per second at high RPMs. I sort of expect the Hellcat engine flows about the same. While it doesn't need as much oil for the OHV hardware, it has more main and rod bearings and more cylinder oil jets to supply with oil.
 
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