Loss of power and its relation to Oil viscosity

[kickster]

Is there any dyno proven significant loss of power as oil viscosity goes up?

Theoretically how much power does oil pump uses to flow different viscosity oils? Has anyone done a test to estimate the power consumption of different viscosity oils?

 

[ekpolk]

I'm pretty sure it's out there, but I don't have it. I do know that in certain situations (qualifying, for example) racing teams will use lower vis oils specifically to achieve the n-th degree of performance over fairly short durations. How much of a difference, I don't know. Experts should be chiming in shortly. . .

 

[Patman]

The problem with dyno testing different viscosities is that you'd probably only see 3-4hp difference between them on a 300hp engine, but yet you'll see more of a variance than that when you dyno test just based on the different conditions between runs. Plus you'd need to make sure the oil temperature is identical on each of the runs. For instance, if you test a 20w50 with a 300F oil temperature it would probably show more horsepower than if you dyno tested a 10w30 with a 180F oil temperature.

 

[MolaKule]

The more horses you have to work with, the less variances in Hp loss you will see on a dyno verses viscosity.

However, you will usually see higher oil temps when using high viscosity fluids, since more ponies are being put into the oil to move it around the engine.

A rule of thumb for daily driver vehicles is to use the least viscosity oil your engine can tolerate commensurate with least wear.

Experimentation with various oils and accurate UOA consultations with Dyson is a good way to determine which oil might be best.

 

[AcuraSLX]

I read a report by Stirling Moss (old racer) that mentioned using the thinnest gear oil made in the running gear to make qualification times better for the Monte Carlo Rally. The car in question was a Sunbeam sedan. They sacrifice the rear end etc, for the qualification. This may not be practical in your car.
Molakule;
Might low viscosity oil make a difference in bhp when you are dealing with a high friction engine? Like a GM 454 CI?

 

[tdi-rick]

Dynoed various oil grades over ten years ago in a Formula Ford (1600cc, approx. 110 HP) engine on a Superflow dyno.

Significant horspower gains (for that category) where you'd sell your granny for 1 HP

We ended up running NEO 0w-5 as it was a consistent 4-5 HP and 4-5 lbs/ft better right through the rev range than what most were then using. (BP Corse 30 SAE30, Castrol Formula R 25w-50)
Over 25*C I'd use a NEO 10w30, that was only about 1.5-2 HP worse. We also ran stupid low oil pressure, 30 PSI @ 7000 RPM.

Also ran 7w gear oil in the Hewland transaxle for qualifying and cold weather, 75w-90 the rest of the time.

Rick.

 

[MolaKule]

quote:

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Might low viscosity oil make a difference in bhp when you are dealing with a high friction engine? Like a GM 454 CI?

---

Since I am referring to daily drivers and light trucks, not racing engines, the rule of thumb (and a pretty good one) is to use the lowest viscosity oil you can that shows low wear UOA's and lowest oil consumption (good ring sealing). That usually means the starting grade to be a 10W30 and work either up or down from there.

An engine with high tension rings will benefit from a lower viscosity oil in terms of reduced Hp, but how much wear do you want and how much blowby can you tolerate?

 

[tdi-rick]

Following on from Molakule re road vs race, I should have added, I use 5w-40 in our two road vehicles, which are turbo diesels.

I should also add that significant changes had to be made to bearing clearances and cylinder bore suface finish to reduce wear in the little Ford engines when using the 0w-5 oil, and I was using the lowest tension ring sets I could buy.

...and seeing as I come from the land where it's common for people to use 25w-70, I still baulk at 10w30's in road engines.

 

[Shannow]

From the September 2004 issue of Australian 4WD Monthly.

4.8l petrol Nissan Patrol on a rolling road dyno
Synforce 15w40 143.9hp
Valvoline 20W-50 140.9hp
Nissan 20W-50 138.9hp
Castrol 10W-40 138.3hp
Penrite 20W-60 138.2hp

3.0l Turbodiesel Toyota Prado
Synforce 15w40 68.8hp
Castrol 10W-40 67.3hp (test 2)
Valvoline 20W-50 66.4hp
Castrol 10W-40 66.1hp (test 1)
Toyota 20W-50 66.1hp
Penrite 20W-60 63.7hp

The castrol oil was Magnatec and used as the reference oil to test for repeatability (maybe not a good idea given some of Castrol's claims)

The Synforce advertises utself as one of the only oils that meets Japanese manufactured turvbodiesel requirements. It looks like it's got either graphite or moly floating in it.

I've noticed a big mileage improvement (1.2MPG)in my Navar going from 15.8cst group 1 to 14.7cst group IV. Next oil change is a 12.7cst group IV, so it will be interesting.

 

[Dr. T]

Yes, I thought there was a link recently to a study in which diffferent grades were dyno tested for hp.

However, I think there's more to it than just viscosity. Yes, ultimately a thinner oil will yield more hp. But, if it's shearing down it may lose it lubricating properties leading to increased friction. Rapid depletion of addatives may also increase friction as well.

Likewise, breakdown leading to sludge, varnish and deposit formation may also increase friction and hp.. Conversely, hp may be lost due to compression loss due to blow-by with a too thin of a lubricant.