Does thickness of the oil matter on a performance application?

[Stopsign32v]

I've always thought that you have to run the weight oil you should run or else you will spin a bearing and your motor will be toast. But I'm here to ask, is that not the case? I've watched this episode and now I have more questions than before and I've also been told by people with similar engines as mine that with a turbo setup pushing hard you want to step up a little on the weight due to the heat it will see.

So if your motor is built for 10W-40 would you be doing damage by going to 20W-50? This is assuming southern state in the warmer weather months.

 

[Rand]

Your question is too generically put to get a simple answer.

it depends on the actual engine, use of engine, and temps the engine runs at etc.

as to if it matters or not. you cant hurt an engine going thicker...(generally)
and with common sense .. no reason to put 25w70 in your 0w8 toyota etc.

are you talking a prius or a built 350 in a track car.. etc.

 

[Fa24wrx]

One consideration in performance is thicker oil will generally lower (slightly) horsepower output

 

[oil pan 4]

Peak oil temps dictate viscosity, unless you have trouble maintaining oil pressure when hot at idle.
Usually you want 20 weight oil for oil temps that stay below 190f all the time.
30 weight for 190 to 230f.
40 weight for 220 to 260f.
50 weight if you see higher than 250f regularly.
My dodge Dakota hits about 210 so it gets a 30 weight.
My riding lawnmower hits about 300f and my pressure washer hits 280f so they gets 50 weight.
Going too thin will weld a rod bearing to the crankshaft.

 

[scrllock]

On the average commuter/city car, the common wisdom is that most wear is from cold starts. Low viscosity for quick flow.

In a performance application, cold starts are much less of a concern than transient oil pressure/film thickness losses. You don't go too high since you just end up creating more heat/power losses. Hence most people just running a step up from the engine sticker.

 

[burbguy82]

 

[Stopsign32v]

Your question is too generically put to get a simple answer.

it depends on the actual engine, use of engine, and temps the engine runs at etc.

as to if it matters or not. you cant hurt an engine going thicker...(generally)
and with common sense .. no reason to put 25w70 in your 0w8 toyota etc.

are you talking a prius or a built 350 in a track car.. etc.

It's a Honda 4 cylinder. It sees 8,500rpms shift point but can rev as high as 9,500rpms. It's turbocharged and sees about 25psi of boost. Power is around 500whp but later will probably go to a bigger turbo and see 700whp.

My issue that I have and always have had is the fact that the cam system is flat tappet so I want an oil with good (I guess you guys call it) film strength? I want to make sure to have a film of oil between metal throughout the system.

 

[cheesepuffs2]

It's a Honda 4 cylinder. It sees 8,500rpms shift point but can rev as high as 9,500rpms. It's turbocharged and sees about 25psi of boost. Power is around 500whp but later will probably go to a bigger turbo and see 700whp.

My issue that I have and always have had is the fact that the cam system is flat tappet so I want an oil with good (I guess you guys call it) film strength? I want to make sure to have a film of oil between metal throughout the system.

Street driven, or strip car?

 

[thescreensavers]

One consideration in performance is thicker oil will generally lower (slightly) horsepower output

That's not true due to better oil ring sealing. There are a few vids on that

 

[Stopsign32v]

Street driven, or strip car?

That doesn't matter, but street driven with hard use occasionally

 

[Stopsign32v]

That's not true due to better oil ring sealing. There are a few vids on that

Correct

 

[cheesepuffs2]

That doesn't matter, but street driven with hard use occasionally

How does that not matter? I asked because if this is a dedicated strip car that gets trailered to the track then you might see surprisingly low oil temps, as 1/4 mile cars don't have enough time usually to build that high of oil temps over the course of one pass at a time. Lower average oil temps would have you wanting to go on the thinner side in viscosity. Generally speaking, a Honda planned to make 700 HP is usually going to be a strip application on slicks, which is why I asked.

 

[cheesepuffs2]

That's not true due to better oil ring sealing. There are a few vids on that

That's only when the rings are worn and the thicker oil creates a better seal that can over-compensate for the increased pumping losses from the thicker viscosity. If the engine is fresh/sound, thinner will always make more power.

This is why racecars use very thin "qualifying oils" to maximize power for one or two laps, and then switch to a thicker oil for a 500 mile race where durability is worth the slight loss in power.

 

[ka9mnx]

One consideration in performance is thicker oil will generally lower (slightly) horsepower output

That theory was debunked in a more recent dyno video. As it was debunked by the posted video.

My Ranger is far from having worn cylinders or rings. Seat-of-the-pants but dyno shows an increase in torque with a very slight loss in mpg in colder weather going from 5w-30 to 0w-40.

BTW. oil is specified by grade. Not weight. Weight is something shippers are concerned about.

 

[Snagglefoot]

On the average commuter/city car, the common wisdom is that most wear is from cold starts. Low viscosity for quick flow.

In a performance application, cold starts are much less of a concern than transient oil pressure/film thickness losses. You don't go too high since you just end up creating more heat/power losses. Hence most people just running a step up from the engine sticker.

It’s absolutely common to see a 0w40 recommended in high performance engines and it’s common that 15w40 is no longer recommended in some Diesel engines, the recommendation going to 5w40.

That theory was debunked in a more recent dyno video. As it was debunked by the posted video.

My Ranger is far from having worn cylinders or rings. Seat-of-the-pants but dyno shows an increase in torque with a very slight loss in mpg in colder weather going from 5w-30 to 0w-40.

BTW. oil is specified by grade. Not weight. Weight is something shippers are concerned about.

This has been discussed at Bitog. You are correct but it was deemed that weight and grade get interchanged enough that we should fogetaboutit.

 

[burbguy82]

It’s absolutely common to see a 0w40 recommended in a high performance engines and it’s common that 15w40 is no longer recommended in some Diesel engines, the recommendation going to 5w40.

This has been discussed at Bitog. You are correct but it was deemed that weight and grade get interchanged enough that we should fogetaboutit.

some just look for that "gotcha" moment.

indeed

 

[kschachn]

So if your motor is built for 10W-40 would you be doing damage by going to 20W-50? This is assuming southern state in the warmer weather months.

No engine is "built" for a certain grade. And as long as a 20W winter rating is appropriate for your starting temperature then it is fine. And as others have noted it's not weight it is grade. And it's HT/HS that matters.

Good variation on the thick vs. thin debate.

 

[kschachn]

View attachment 261659

Beat to death, turned over and beat again.

 

[Stopsign32v]

No engine is "built" for a certain grade. And as long as a 20W winter rating is appropriate for your starting temperature then it is fine. And as others have noted it's not weight it is grade. And it's HT/HS that matters.

Good variation on the thick vs. thin debate.

But the main clearances and such dictate what oil the motor is designed for, no?

 

[scrllock]

It’s absolutely common to see a 0w40 recommended in high performance engines and it’s common that 15w40 is no longer recommended in some Diesel engines, the recommendation going to 5w40.

Ok. Those are all 40 grade oils. OP is discussing moving from a 40 grade to a 50 grade.

So if a motor was built "for 10W-40" would there be any negative


But the main clearances and such dictate what oil the motor is designed for, no?

If your motor has been rebuilt and someone gave you an oil spec to run with your motor's clearances, I would follow that recommendation. It's safe to say most engine rebuilders aren't really erring on the side of fuel efficiency (and probably assume you're putting some heat into your built engine).

This has also been beaten to death, but in a performance application, you should care more about HTHS than whatever grade your KV100 classifies it as. In this case, it's a street car. You have an oil recommendation from the builder. Not much reason to overthink it. Maybe err on the side of high ZDDP for the cam, but I'm sure there are options for that in 10w40.