oil weight for forced induction

[DesertFrs]

I'm using PurÖl elite 0w-20 on mine. Till this day I don't believe their enough clearance for anything thicker

[BRZPDX]

I'm sticking with ow-20 as well for street.

[carlossanchez89]

Motul 5-40

[Reaper]

Amsoil 5w30 dominator. Subaru recomends 5w30 for the turbo fa20dit.

[cjsporl1996]

I think the best way to judge the best oil weight is to look at the blueprint of the engine. Someone must know the clearance. Although if they are using 5w30 on the new fa20 wrx that's probably the best way to go.

[CSG Mike]

Remember, even with FI, engine tolerances haven't changed. If your oil is properly cooled...

[Element Tuning]

We know that any high end synthetic is going to "lubricate" the engine surfaces properly but common sense should lead you to make some judgement calls on the OEM oil viscosity with OEM HP levels of 150 whp on my dyno compared to 400 whp on the same dyno.

The biggest concern in any engine is going to be the force from the piston and rod being exerted on the "oil wedge" between the rod, rod bearing, and the crank. So the force being exerted on that oil wedge at 150 whp is not the same as the force trying to squeeze that oil out of the bearing at 400 whp. So many don't understand the job of the crank and rod bearings is not to act as bearings but to maintain the oil wedge which is the actual bearing.

Now track guys are seeing huge oil temps so oil pressure can drop significantly at these temps so cooling and increasing viscosity under these conditions is critical in maintaining high oil pressure so this "oil wedge" is maintained.

Look at the boosted guys who have spun bearings and realize they didn't have enough oil pressure to maintain the wedge and that's why the bearings failed so take note of their oil weights.

I'm on Redline 40w Race for racing and on a 10w40 for street as I know exactly how much oil pressure is required to keep from squeezing out the wedge on an STi motor. Problem is on the FA the rod bearings are narrower and therefore I know more pressure per square inch will be required than on our STi race engines.

Synthetics flow so well these days at cold temps you would be surprised at how a higher viscosity can still work well for street where OEM/EPA fuel/emissions requirements are not your requirement.

My 2c.
Phil Grabow

[cdrazic93]

@AVOturboworld @Drift-Office

Paul and Bob, what oil are you guys using?

[lexusb3]

Originally Posted by Element Tuning

We know that any high end synthetic is going to "lubricate" the engine surfaces properly but common sense should lead you to make some judgement calls on the OEM oil viscosity with OEM HP levels of 150 whp on my dyno compared to 400 whp on the same dyno.

The biggest concern in any engine is going to be the force from the piston and rod being exerted on the "oil wedge" between the rod, rod bearing, and the crank. So the force being exerted on that oil wedge at 150 whp is not the same as the force trying to squeeze that oil out of the bearing at 400 whp. So many don't understand the job of the crank and rod bearings is not to act as bearings but to maintain the oil wedge which is the actual bearing.

Now track guys are seeing huge oil temps so oil pressure can drop significantly at these temps so cooling and increasing viscosity under these conditions is critical in maintaining high oil pressure so this "oil wedge" is maintained.

Look at the boosted guys who have spun bearings and realize they didn't have enough oil pressure to maintain the wedge and that's why the bearings failed so take note of their oil weights.

I'm on Redline 40w Race for racing and on a 10w40 for street as I know exactly how much oil pressure is required to keep from squeezing out the wedge on an STi motor. Problem is on the FA the rod bearings are narrower and therefore I know more pressure per square inch will be required than on our STi race engines.

Synthetics flow so well these days at cold temps you would be surprised at how a higher viscosity can still work well for street where OEM/EPA fuel/emissions requirements are not your requirement.

My 2c.
Phil Grabow

And ppl called me crazy for using 10-40w thank you lol

[cdrazic93]

Originally Posted by lexusb3

And ppl called me crazy for using 10-40w thank you lol

Well, logically thinking after a certain level of power, the OEM oil won't be able to hold up to the increase of pressure and heat, requiring a thicker weight oil. Question is, which is best. No one would know until someone does a tear down of two engines at the same hp driven for the same miles using different oil.

[King Tut]

Originally Posted by cdrazic93

@King Tut @jamesm @Calum @Sportsguy83 @Frs300

I ran Amsoil Signature 0w20 in mine.

[cjsporl1996]

I can't see how a 10w40 in this engine is a good idea at all. I mean I run a 10w40 in my Chevy 350 that puts out 320 whp and 360 pounds of torque at the wheels. We need a engineer on this forum lol.

[Sportsguy83]

What worries me on this higher weight oil is that engine clearances don't change after you boost it like @CSG Mike said.

It worries me that heavy oil will not be able to make it inside the tight clearances under all conditions. The goal of oil is for it to be present between metal parts and prevent them from contact.

The way I see oil is, the thinnest possible that will not break down at the intended use temperature.

What benefit is there from running 10-XX from 0-XX when COLD? I see none.

The advantage a XX-40 would have over an XX-20 is resistance to break down at higher temperatures which can be achieved with a good oil cooler keeping those temperatures in check.

I would agree for extreme conditions, a 5-30 would be an acceptable choice. But why go higher than that if you have an oil cooler that will keep oil temps below 230 at the worst possible?

I'm willing and open to reading/learning other people's knowledge on the subject.

[cdrazic93]

would a 0w-40 be any different than a 5w-30?