Oil Weight for built engine/Ideal oil pressures

[Only1Hockeytown]

Hi all, I drive a 2006 Evo with a built engine. I built it myself so I have no builder I can ask this question.

Conventional wisdom says run a thicker than usual oil as the oil clearances on a built engine are generally greater than stock built engines. Originally I went with 20w-50 oil and dropped down to 5w-50 oil for the winter. I ended up having to put in 5w-30 oil and at the same time I installed an oil gauge.

I didn't have an oil gauge for the previous oil weights but on my current 5w-30 oil, my oil pressure is around 100psi on initial start up and idles at around 20 once fully warmed up. I'm not worried about those oil pressures (I'm sure it's better to have too much than too little) but I'm thinking that at 5w-30, those oil pressures are pretty fine and I wouldn't want to go for a thicker oil, in fact I could almost go to a thinner oil.

Does that make sense or does anyone disagree? Should I even go to a 0w-20 oil? Also do you think I should just run the same oil through winter and summer? I'm in Michigan so we have a pretty wide range of temperatures throughout the year.

I appreciate the help

 

[Ramblejam]

Evo 9:

Originally Posted By: Only1Hockeytown
I'm sure it's better to have too much than too little


Sure, but flow>pressure, as long as pressure is adequate.

Where are you @ 3,500?

 

[Lasthope05]

You need a thicker oil, not only for the looser clearances but also for the increased amount of heat you're going to produce not to mention the increased load. The thinnest i would go is a 5w40.

This is coming from a guy with a 850whp DSM.

 

[Ramblejam]

Originally Posted By: Lasthope05
You need a thicker oil, not only for the looser clearances but also for tree increased amount of heat you're going to produce not to mention the increased load. The thinnest i would go is a 5w40.


Support that assertion with any data. PLEASE!

Not theory or conjecture.

 

[Lasthope05]

Originally Posted By: Ramblejam
Originally Posted By: Lasthope05
You need a thicker oil, not only for the looser clearances but also for tree increased amount of heat you're going to produce not to mention the increased load. The thinnest i would go is a 5w40.


Support that assertion with any data. PLEASE!

Not theory or conjecture.


Let me get this straight. The guy has a turbo engine with a build motor that has looser tolerances than factory and will be outting out more heat/load/sheer forces on the oil yet you believe he should drop a grade from the factory 30 weight? I guess we should be telling the turbo euro cars to stop running 40 weight and just got straight to a 20. Lol. Good luck with that OP if you take his advice.

I work on and build high hp turbo cars. There is a difference between a grocery getter and a hard driven performance car when it comes to oiling needs.

 

[CT8]

Originally Posted By: Lasthope05
Originally Posted By: Ramblejam
Originally Posted By: Lasthope05
You need a thicker oil, not only for the looser clearances but also for tree increased amount of heat you're going to produce not to mention the increased load. The thinnest i would go is a 5w40.


Support that assertion with any data. PLEASE!

Not theory or conjecture.


Let me get this straight. The guy has a turbo engine with a build motor that has looser tolerances than factory and will be outting out more heat/load/sheer forces on the oil yet you believe he should drop a grade from the factory 30 weight? I guess we should be telling the turbo euro cars to stop running 40 weight and just got straight to a 20. Lol. Good luck with that OP if you take his advice.
looser clearances, tolerances are the allowed deviations of the clearances . Oil university educated most likely.

 

[Ramblejam]

Originally Posted By: Lasthope05
Let me get this straight. The guy has a turbo engine with a build motor that has looser tolerances than factory and will be outting out more heat/load/sheer forces on the oil yet you believe he should drop a grade from the factory 30 weight? I guess we should be telling the turbo euro cars to stop running 40 weight and just got straight to a 20. Lol. Good luck with that OP if you take his advice.

As I figured...

You can't actually support your theories with any actual data/evidence. Instead, we get the usual fear-mongering with an added side dish of typical car-guy forum tribology (clearances/tolerances/"sheer" forces).

 

[Shannow]

Originally Posted By: Ramblejam

Sure, but flow>pressure


Flow lubricates ???

Support that assertion with any data. PLEASE!

Not theory or conjecture.

 

[OVERKILL]

Originally Posted By: Lasthope05
You need a thicker oil, not only for the looser clearances but also for the increased amount of heat you're going to produce not to mention the increased load. The thinnest i would go is a 5w40.

This is coming from a guy with a 850whp DSM.


I agree with this guy.

You have more power than stock, subsequently you are heating the oil more than stock. Elevated oil temperatures reduce viscosity, which may mean an increase in viscosity is required to keep parts separated. The same goes with higher than stock power levels in terms of load. I would also run a 5w-40 or 0w-40; something that meets the Euro requirements with an HTHS of >3.5cP at a minimum, see how your pressure looks hot from there. I would not be concerned with what they are at currently, but 20 hot sounds low, and I bet is lower than what the engine made stock since you have opened up some clearances from the sounds of things.

 

[Shannow]

Oil pressure doesn't tell you a thing about what your engine needs.

In a stock engine, the oil pressure, on the grade specified by the manufacturer tells you that you need to take some action with regard to remediating bearing clearances or the like.

There's a (flawed" school of thought that states that you keep dropping viscosity until you reach the manufacturer's minimum, and you'll be OK, but there's not a logical path that you can go down to reach that conclusion from the starting point of stock engine and recommended grade.

It appears that you have opened up clearances over stock, that in and of itself would suggest going thicker than stock, as your mains (and presumably big ends) now have more side leakage to make up.

The oil to your big end bearings has to pass through the mains, through the drillings in the crank to supply the big ends...running low oil pressure reduces this flow (plus flow to any piston squirters if the engine is so equipped).

 

[Ramblejam]

Originally Posted By: Shannow
Originally Posted By: Ramblejam

Sure, but flow>pressure


Flow lubricates ???

Support that assertion with any data. PLEASE!

Not theory or conjecture.


If you're going to quote me, do so with the full quote...don't parse it in lame attempt to make it appear I said something I didn't.

 

[Nissan101]

Keep going thin till it starts knocking....then go up a grade

 

[Lasthope05]

Originally Posted By: Ramblejam
Originally Posted By: Lasthope05
Let me get this straight. The guy has a turbo engine with a build motor that has looser tolerances than factory and will be outting out more heat/load/sheer forces on the oil yet you believe he should drop a grade from the factory 30 weight? I guess we should be telling the turbo euro cars to stop running 40 weight and just got straight to a 20. Lol. Good luck with that OP if you take his advice.

As I figured...

You can't actually support your theories with any actual data/evidence. Instead, we get the usual fear-mongering with an added side dish of typical car-guy forum tribology (clearances/tolerances/"sheer" forces).


LOl So if the OP uses a 0w20 based on your recommendation, will you guarantee he will not have an oil relate failure? Where is your data/evidence that supports that a 0w20 applicable to his specific situation?

I work on these engines and the older DSM cousins. Where does your knowledge come from on this specific car?


BTW OP. What are the actual clearances you have to the mains and rods? Did you delete the balance shafts or left them?

 

[Only1Hockeytown]

Thanks for all the replies.

My memory is lacking but they're around .002-.0025. Balance shafts were left in and I do have piston squirters. Pressure around 3500 and up is per spec.

Makes sense the oil pressure is not the be-all end-all. Sounds like I should definitely not go thinner. Would 0w-40 perhaps be a good spot, or maybe go back to the original 5w-50?

Again thanks for all the replies and the educations

 

[aquariuscsm]

I'd just stay with the 5W50.

 

[OVERKILL]

Originally Posted By: Only1Hockeytown
Thanks for all the replies.

My memory is lacking but they're around .002-.0025. Balance shafts were left in and I do have piston squirters. Pressure around 3500 and up is per spec.

Makes sense the oil pressure is not the be-all end-all. Sounds like I should definitely not go thinner. Would 0w-40 perhaps be a good spot, or maybe go back to the original 5w-50?

Again thanks for all the replies and the educations

A 0w-40 will provide excellent cold temperature performance with a higher HTHS (high temp, high sheer) viscosity keeping parts separated. It is a solid choice.

 

[Only1Hockeytown]

Looked up the build sheet, .0018 on rods and .0023 on mains.

 

[Ramblejam]

Originally Posted By: Shannow
Oil pressure doesn't tell you a thing about what your engine needs.


We'd strongly disagree.

Originally Posted By: Only1Hockeytown
Looked up the build sheet, .0018 on rods and .0023 on mains.


I have the FSM right in front of me; amusing to see all the talk on the last page of "looser clearances".

 

[Shannow]

Originally Posted By: Ramblejam

As I figured...

You can't actually support your theories with any actual data/evidence. Instead, we get the usual fear-mongering with an added side dish of typical car-guy forum tribology (clearances/tolerances/"sheer" forces).


Theory eh ?

OK, here's a bearing design curve, with MOFT (minimum oil film thickness - it's what keeps the parts apart), versus various bearing parameters.

The numbers down the bottom are
r = shaft radius
c = bearing clearance
u = kinematic viscosity
N = Revolutions Per Second
P = bearing load, divided by the projected area.

Pick a point, any point on the L/D=14 line (that's a bearing of width 1/4 times the diameter, closest to engine mains for example).

Increase the "P" by increasing cylinder pressure, i.e. power output at the same RPM, and the minimum oil film thickness claearly reduces...the only variable that the OP has to get this back is viscosity greater than the stocker.

Increase the bearing clearances, and AGAIN, the MOFT is reduced...and again, the only way to recover, all things being equal is viscosity.

Yes, the stocker HAS a safety margin, but by increasing clearances and cylinder pressure you are reducing it.

Neither of us (nor the other two thinwits) know where that margin IS on a modified engine with more power, so the safe recommendation is to go thicker than stock.

What we DO know is that the OP has lower then recommended oil pressure (for a stock engine, stock clearances, with OEM recommended grades)... from this, we can deduce that the clearances are opened up some.

Why ?

this is the side leakage chart in bearing design...at idle, N is the same, P is the same, so you can only deduce that "C" the radial clearances have opened up somewhat, giving an increased (moved to the left) oil flow.

The oil pressure is an artifact of the pump supplying more pressure than the bearing needs/is drawing from the galleries...less bearing side leakage, the less it draws from the galleries, and the higher the oil pressure.

FLOW doesn't lubricate, oil viscosity and bearing design ensure MOFT is designed and maintained, and flow happens as a result of the design process.

 

[Lasthope05]

A 40 weight would work well for your bearing clearances and likely so will the 50 weight. The big thing is making sure you the oil you want to run has a high zddp content(which it most likely will since there is no zinc restrictions). I run looser in my motors at 0.0025 and switch off between bran penn or VR-1 20w50.

Are you still on the stock turbo or aftermarket? Just saw your post of the updated clearances. With a .0018 rod and .0023 main I would stick to a 40 weight depending on your power goals.