[Bill Meyer]

Yesterday I dynoed my bracket engine. I've had the same engine for 12 years now, with the same heads,cam,carb etc. I had to change the block once, but moved all the parts. This engine has always made 670ish HP and 620ish TQ, so the session was to be quick and simple-just a good breakin and make sure of no leaks etc, so I had some extra time to try some things.
Final pull w/15/40 Rotella T (old stuff) TQ=628@5000 HP=675@6400

Since I was going home and changing the oil & filter before going racing, I thought I would do it on the dyno and see how much ole reliable would gain using what I normally run.

Test pull w/NAPA 5-30 full synthetic TQ=623@5000 HP=664@6400

Something had to be wrong-so we made sure the water and oil temps were identical to the final pull and did it again - same result!!

Now being the Pete McCarthy fan, and faithfully reading his book, I had always thought that thinner oil and synthetic would automatically get you some more HP.

After pressing the experienced Dyno operator, Ron, @ R&R dyno, he said "I could have told you that you would lose by going to synthetic, but I thought the thinner oil would have helped some. No one has ever gotten more HP with synthetic as I have done this test many times"

Not only were the peaks smaller, but the averages were as well:
Torque 4300-6400 avg 606 vs 598
Horsepower avg 627 vs 618

Interesting!! - Bill-

[lakefect]

so did u put the 15w40 back in and make another pull?
something else might have caused this , i could see no increase but iam not buying that much loss in hp

i will stick with my redline syn.

[Half-Inch Stud]

I doubt because I lack understanding how 5Warm-30cold SYNTH would lose to 15Warm-40cold conventional on a run-in engine.

Let's bust this down:

Change in bearing/journal friction: NO.
Change in Oil Pump drag: NO
Change in CYL sealing: SUSPECT (see any blowby, crankcase vac/pres difference?)
Change in windage from oil volume difference: SUSPECT (see any PSI gauge fluctuation?)
Change in combustion contamination: SUSPECT
What else is there?
================================================== ======
How exactly was the oil volume kept identical?
How steady did the Oil gauge look?
Any change in blowby?
Any pinging?

[BruceWilkie]

Originally Posted by Half-Inch Stud

I doubt because I lack understanding how 5Warm-30cold SYNTH would lose to 15Warm-40cold conventional on a run-in engine.

Let's bust this down:

Change in bearing/journal friction: NO.
Change in Oil Pump drag: NO
Change in CYL sealing: SUSPECT (see any blowby, crankcase vac/pres difference?)
Change in windage from oil volume difference: SUSPECT (see any PSI gauge fluctuation?)
Change in combustion contamination: SUSPECT
What else is there?
================================================== ======
How exactly was the oil volume kept identical?
How steady did the Oil gauge look?
Any change in blowby?
Any pinging?

Oil temperature. (water temp too) Would have also liked to see same grade/weight and brand synthetic vs conventional.

Fresh oil needs to be compared too. Old oil, especially non synthetic breaks down just sitting. (All oils will breakdown eventually) Especially exposed to temperature changes of summer through spring. (even in unopened containers)

Plenty of good info about oil starting here... http://www.bobistheoilguy.com/motor-oil-101/ A long read (10 sections) but plenty of need to know facts.

[Jeff Kinsler]

thinner oil will make more hp.. the oil temps make a difference..

[Half-Inch Stud]

Seems we're in agreement, except for the Original Posted DATA...

[mike leech]

It's possible the rings weren't fully seated when the switch took place. For it to lose that much it sure isn't oil drag that accounts for the difference.

[gman005]

I dont remember the exact hp and torque gains but i definitly made more power with 5w 30 mobil 1 versus the castrol 10w 40. Just my 2 cents

[Bill Meyer]

Guys, I brought this up because I too didn"t believe it.

Lakefect - I wish I had kept the old oil as I would have put it back in for some solid proof.
H.I.S. - some good comments/questions as usual. - Suspects:
A. Combustion sealing - If anything it should have gotten better. I did check the vacuum numbers (had a guage on the evac system) 3.2" both pulls, identical
B. Volume difference - posible, but I have had the same pan for 12 years and put in the same 7 1/2 qts. Oil level is adjusted at the track (added if oil pressure drops on hard braking)
C.Oil pressure 15/40 avg 78.4 PSI - 5/30 avg 61.6 so less power required to move thinner oil - sounds right?
D. Change in combustion contamination ?????? A/F ratos very similiar

The only thing that I can figure out maybe - The room temp during the conventional pull shows as being 78 degrees. This was the 10th pull of the session with very little down time. The room temp after the oil change is shown as 68 degrees. Perhaps this room temp variation is enough to alter the correction factors. Cooler air requires less correction? If someone knows for sure how the correction factors are calculated, please chime in - otherwise, I will try to find out next week if this could be the cause.

[Half-Inch Stud]

Originally Posted by Bill Meyer

Guys...I too didn"t believe it.

Lakefect -...H.I.S. -...- Suspects:
B. Volume difference - posible...
C.Oil pressure 15/40 avg 78.4 PSI - 5/30 avg 61.6...
...maybe - The room temp during the conventional pull shows as being 78 degrees...room temp after the oil change is shown as 68 degrees...

C. 61.6 PSI Synthetic vs Conventional 78.4 PSI. That remains a clue.
Combine Oil Pressure Difference with Room Temp differnece, throw a little Oil volume difference in there; Perhaps a combination of such can cause the Dyno-Diff.

[aaronman]

Very interesting post. I don't understand dyno correction factors but 10 degrees of intake air temp change from 78 degrees to 68 degrees is equivalent to ~800 feet of density altitude assuming everything else is the same.

[Steve C.]

We have always started out on the dyno with regular oil then after a few pulls switched to synthetic oil along with a filter change. In every case there has always been a increase in power with the synthetic oil. I used to use Mobil 1 now we use Redline synthetic.




.

[65nss4spdGTO]

Originally Posted by Bill Meyer

The only thing that I can figure out maybe - The room temp during the conventional pull shows as being 78 degrees. This was the 10th pull of the session with very little down time. The room temp after the oil change is shown as 68 degrees. Perhaps this room temp variation is enough to alter the correction factors. Cooler air requires less correction? If someone knows for sure how the correction factors are calculated, please chime in - otherwise, I will try to find out next week if this could be the cause.

Bill,

Do you have the dyno sheets that show measured power? I like to look at those numbers when things don't seem to make sense.

Calvin Hill
Hill Performance / Mondello Tech Center
708-250-7420

[Bill Meyer]

I spoke with the dyno operator yesterday. He confirmed a few things for me as well as confirming our findings on the synthetic oil.

The room temp(input air) is a factor in the correction formula.

A 9 degree temp swing is worth about 1 percent HP... 675 hp x .01= 6.75

Raw (uncorrected) data showed @6400 petroleum 630.7 HP
synthetic 629.1 HP
Since the room had cooled off, the correction factor was't as big, thus the 11 HP difference.

Once again, I have nothing in this other than to report something I tried on the dyno.
I too am surprised, but may not spring for synthetic this year.

[Half-Inch Stud]

Originally Posted by Bill Meyer

... @6400 petroleum 630... synthetic 629.1 HP... the room had cooled off, the correction factor....but may not spring for synthetic this year.

Prevailing evidence favors synthetic AFTER rings have seated, CYL walls true-ed up. so, you got time.