HP V Viscosity=Not Much

[rrounds]

Car Craft has a article on a 6.0L LS engine that put out 505 HP and 475 TQ with 10/40 oil at 200 degree engine oil temp.
Switched to Lucas 5/20 race oil and at the same 200 degree oil temp it ran 509 HP with 477 TQ.
The LS did have very high oil pressure, 97 psi with the 10/40 and it still had 85 psi with the 5/20 @ 200 degrees.
They said they are going to pull the oil pump and see why it has such high oil pressure, because running that high pressure does rob HP.

I thought that the HP difference would have been greater than 5 HP and 2 lb ft of TQ going from a 10/40 to a 5/20 oil.

ROD

 

[CT8]

Rookie move the oil is at 200*f. Then the protection has to be considered. while the difference at operating temps is small is makes a great difference. Think about how much gas a 5 hp lawn mower used. We are talking about 5 hp between the 20 and 40 oil? Is all the cars in the nation used 20 oil there would be lots of gas saved per day. That is what the CAFE are about.

 

[ZeeOSix]

Originally Posted by rrounds
Car Craft has a article on a 6.0L LS engine that put out 505 HP and 475 TQ with 10/40 oil at 200 degree engine oil temp.
Switched to Lucas 5/20 race oil and at the same 200 degree oil temp it ran 509 HP with 477 TQ.
The LS did have very high oil pressure, 97 psi with the 10/40 and it still had 85 psi with the 5/20 @ 200 degrees.
They said they are going to pull the oil pump and see why it has such high oil pressure, because running that high pressure does rob HP.

I thought that the HP difference would have been greater than 5 HP and 2 lb ft of TQ going from a 10/40 to a 5/20 oil.

ROD


No surprise on the HP gain due to thinner oil. A 4HP gain (509 from 505) is 4/505 = 0.8%.

The HP lost in the oil pump is minuscule. Pump HP = (PSI x GPM)/1714. At redline, the pump is putting out around 8 GPM, so at 97 PSI it would take 0.45 HP to pump the 10W-40. It would take 0.40 HP to pump the 5W-20 ... so the pump ate up a whole whopping 0.05 HP with the 10W-40.

 

[CR94]

^ divided by the pump efficiency, which isn't 100%

Most of the power difference was in bearings, not the pump.

 

[Shannow]

This thread makes me happy.
More people are getting it

 

[bullwinkle]

Now you see why NASCAR uses 0W5 race oil or similar-every little bit of power gained counts! Of course, when you rebuild your engine every 500 miles...

 

[SOHCman]

Originally Posted by CT8
Rookie move the oil is at 200*f. Then the protection has to be considered. while the difference at operating temps is small is makes a great difference. Think about how much gas a 5 hp lawn mower used. We are talking about 5 hp between the 20 and 40 oil? Is all the cars in the nation used 20 oil there would be lots of gas saved per day. That is what the CAFE are about.


That 5HP was found at peak RPMs. There might be no difference at all HP wise at normal highway RPMs, and if there is a difference it's miniscule. I'm running 10w-30 in my 5w-20 engine and have not seen a milage difference personally, YMMV.

 

[CT8]

The gain is so tiny I have never been able to detect a difference by changing the oil viscosity.

 

[FCD]

I believe Motor Trend did an experiment regarding this on a typical Small Block Chevy 350.

They found the engine lost 3 horsepower on 20W-50, compared to i believe 5W-20.

 

[jhellwig]

Originally Posted by CT8
The gain is so tiny I have never been able to detect a difference by changing the oil viscosity.

I would also question the accuracy of the Dyno. .8% difference would be pushing the combined accuracy of the measurement equipment. It would be nice to know the how may runs on each they preformed and what the numbers were

 

[Patman]

I also question the repeatability of dyno numbers, as I have had a few cars dyno tested over the years and horsepower can vary a lot (5-10 rwhp) from one run to the next, it's never identical to the previous pull.

 

[RDY4WAR]

What about internal engine cooling? Wouldn't the easier flowing lower viscosity be able to pull more heat out of the bearings, crank, and rods?

 

[CR94]

Originally Posted by RDY4WAR
What about internal engine cooling? Wouldn't the easier flowing lower viscosity be able to pull more heat out of the bearings, crank, and rods?
More importantly, less mechanical power will be converted to heat through shearing the oil in those places, so the oil temperature should be a tad lower. (Assuming hydrodynamic regime continues.)

 

[Shannow]

Originally Posted by RDY4WAR
What about internal engine cooling? Wouldn't the easier flowing lower viscosity be able to pull more heat out of the bearings, crank, and rods?


That's the next part of the education...the power losses demonstrated are due to the shearing of the lubricant...and that's what cretes the heat in things like bearings and piston skirts.

The belief that "freer flowing" (it isn't the pumps are positive displacement) oil "carries away more heat" is pervasive, and everywhere...was in Motor Oil University for over a decade, and the purveyor still claims it as fact.

See in these, that the heat flow is FROM the bearing into the crank, rods, and block

 

[Shannow]

And per this one...the differences in each bearing from 0W20 to 20W50 are tenns to hundreds of watts (per bearing).

So you can't expect to see a dozen horsepower as the result of an oil change...and I chellenge anyone who states that their car feels "sluggish" on an ILSAC 30 over a 20 to get their butt dyno properly calibrated...it's psychosomatic.

 

[RDY4WAR]

Interesting. I was thinking of it like heating radiating down the pistons and rods from combustion.

 

[Gokhan]

Originally Posted by Shannow
And per this one...the differences in each bearing from 0W20 to 20W50 are tenns to hundreds of watts (per bearing).

So you can't expect to see a dozen horsepower as the result of an oil change...and I chellenge anyone who states that their car feels "sluggish" on an ILSAC 30 over a 20 to get their butt dyno properly calibrated...it's psychosomatic.

Wow. Really?

Taken without context at its worst.

What you posted is referring to only the viscosity-related losses at the connecting rods, not the total viscosity-related loss.

Here is the full paper. The total viscosity loss from 0W-20 to 20W-50 in the urban cycle is about 700 W (~ 1 horsepower), not 70 W. This is more like ~ 5% or more in fuel economy, not 0.05%. Drivers would take the 5% ($$$ annual fuel-cost savings) and the racers would take the 1 HP or more.

2002-01-3355
Lubrication, Tribology & Motorsport
R.I. Taylor
Shell Global Solutions (UK), Cheshire Innovation Park, PO Box 1, Chester, CH1 3SH, UK
Click here for the PDF paper

 

[Shannow]

Originally Posted by Gokhan
Originally Posted by Shannow
And per this one...the differences in each bearing from 0W20 to 20W50 are tenns to hundreds of watts (per bearing).

So you can't expect to see a dozen horsepower as the result of an oil change...and I chellenge anyone who states that their car feels "sluggish" on an ILSAC 30 over a 20 to get their butt dyno properly calibrated...it's psychosomatic.

Wow. Really?

Taken without context at its worst.

What you posted is referring to only the viscosity-related losses at the connecting rods, not the total viscosity-related loss.

Here is the full paper. The total viscosity loss from 0W-20 to 20W-50 in the urban cycle is about 700 W (~ 1 horsepower), not 70 W. This is more like ~ 5% or more in fuel economy, not 0.05%. Drivers would take the 5% ($$$ annual fuel-cost savings) and the racers would take the 1 HP or more.


Mind telling us all what you are replying to and claim is taken out of context ???

I claimed tens to hunderds of watts ...per bearing...I didn't discount piston friction, of course it's there...there's hundreds of watts, not dozens of horsepower.

And if YOU can notice 1hp difference (748 watts, comparable to your 700W), then YES, you need your butt dyno recalibrated.

 

[Gokhan]

Originally Posted by Shannow
And if YOU can notice 1hp difference (748 watts, comparable to your 700W),

1 hp is for urban driving. The frictional power is equal to the frictional torque multiplied by the RPM. 5 hp quoted by the OP seems reasonable for high-RPM conditions. 5 hp could make a difference in a race.

And 1 hp in urban driving corresponds to ~ 5% in fuel economy, which is a lot.