quote:

Originally posted by MWrench:

quote:

The minimum oil pressure that an engine needs for lubrication is about 5psi at the bearings. More than that will not get you better lubrication. Less will destroy your bearings!

I do not agree with either of these statements as applied to vehicle engines. Most all of the performance engine builders agree that a minimum of 10 PSI/1000 RPM is need to insure lubrication and prevent engine failure. While pressure isn't the real factor, it is needed to insure that the film of oil between various rotating metal parts is thick enough to provide a barrier and prevent metal to metal contact under ALL circumstances. Turbo charged engines or very high compression engines present more of a lubrication challenge as well.Any brief loss of pressure/oil volume or air in the system will and does cause bearing failure almost immediately.[/QUOTE]

You are definitely allowed to disagree, but make sure you understand the original comment. 5 psi (at the bearing) is all that is needed to keep a journal bearing from failing. In reality the connecting rod bearings are kept away from the crank journal by the hydrodynamic wedge formed by the combination of rotation, pressure and the viscosity of the oil. Here is a nice link that explains it in a little more detail - http://www.phy.davidson.edu/fa...tion/lubrication.htm
In order for the proper hydrodynamic wedge to form all that is needed is a supply of oil to the bearing. The supply pressure is not critical (in theory!).
What you do need is an adequate volume of oil to keep the temperature of the components in the right range. The viscosity of the lubrication fluid is critical in creating the hydrodynamic wedge working. If you don’t have enough flow the oil will continue to heat and get less viscous. Eventually the decrease in viscosity will not support the hydrodynamic wedge and the bearing will contact the journal.

One other thing that should be pointed out is that most engines measure oil pressure at the head of the oil galley. As various feeds branch off the main oil galley (lubrication for cams, lifters, rockers, balance shafts, turbos, piston squirters and anything else being fed pressurized oil) the oil pressure will drop. Typically the oil galley feeds the crank at several locations and then the rod bearings are fed internally from the main bearings. All along this route the oil pressure will be decreasing. Once on the crank the rotational forces can also cause a decrease in the rod bearing oil pressures.

That is where the 10psi per 1k rpm rule of thumb comes into play (I use 1 bar per 1k rpm), it allows for the pressure losses in the oil galleys to be factored in so that the minimal oil pressure at the actual bearing is not compromised….and that pressure is still about 5 psi minimum at the bearing before a failure.
In a way it’s a trick statement to most folks because you don’t have a way to measure the oil pressure at the connecting rod bearing. So you have to come up with a rule of thumb that can be used when looking at the conventional oil galley pressure gauge – that’s where the 10psi of pressure per 1k rpm rule comes from.
BTW – here is a video of a 500hp 2.5 liter race engine I made
http://youtu.be/rbHuDUgLHTE
and a 600+hp 3.1 liter 16v Porsche engine of mine being warmed up
http://youtu.be/q4nevvbHJ9o

quote:

Where else could you pedal an oil for $4 to $5 per gallon in 1968 when Rotella was selling for about $1.70/gallon?

Florida Power and Light installed power peaking turbines, which used J57s as the gas generator (2 each unit) at the Port Everglades plant around 1971. They could have bought our turbojet oil at $7.50/gal (55 gal drum - at the time, Rotella T 30 was $0.86/gal in 55s). Only after they blew two gas generators did they change out all the units to Shell.

$4-5/gal sounds about right for the military price (they used a slightly different product). Synthesizing at the time was a very new science. Where motor oils were blended in 50-100K gal batches, the Shell turbojet oils were mixed in a lab in 1,000-2,500 gallon batches (in lube-making proportions, basically a thimbleful at a time).

The two biggest achievements (IMHO) in motor oil in the past 40 years are inventing processes to mass-produce synthetic base stocks and the creation of shear-stable viscosity index improvers (VIIs)

Rusty, I think the batches we made for initial approval were either 30 or 50 gallon. Really were hand made with the personal touch and real dedication of the full team. I had returned to college full time when they were approved and made the larger batches sent to the Air Force.
We tested a modification for recip aircraft and gave up due to boredom. There was no wear or oil deterioration after 200 hours, twice the normal test. Again, only the possibility of blending with mineral oils could bring the price into competition since oil changes were mandated periods.
As an item of interest the recip test bed was a VW engine sans sheet metal on a dynomometer. We used thermocouples on the pods and placed squirrel cage fans to obtain the desired head temperatures.
I think the neatest test unit was the transmission set-up. It was a 327 with 4 bbl mated with the ho-hum powerglide bolted to a dyno. It did a 90 second idle followed by a full throttle acceleration to 90 mph equivalent then back to idle (repeated for 16 hours, down for 8 then back up for 16 until we finished at 100 hours). Pretty neat standing next to it listening to the carb and exhaust sounds.
A unit not used extensively was a temp room that could go from some uncomfortable below zero to 125F with winds up to 100. Cars could be put in it and cycled.
Not sure we really made profits but the technology and neat stuff was pretty impressive to an undergrad in 1968-9.

Lots of good info here
I use Rotella or Conoco Phillips 15w40 in everything I own. And they're all gasoline engines. Living on Canada's west coast (it's been 50F all winter, maybe 30 overnight) I don't really need a thinner weight oil. What I do like is the ZDDP (zinc) additive for my flat tappet cams.
76 Barth 454
87 Buick Grand National 3.8l Turbo
87 Chev G20 Van 5.7l
90 Lumina APV 3.1l (just a work van)

I don't know if they still are, but years ago, Conoco motor oils were direct Shell rebrands.

quote:

Originally posted by Rusty:
I don't know if they still are, but years ago, Conoco motor oils were direct Shell rebrands.

I'm not sure about that, Rusty. But a sales rep told me that the ZDDP (Zinc dialkyldithiophosphates) content in the C-P is about 1500 ppm and the Rotella is around 1200 ppm. Untill (if ever) I go with a roller cam, it's the only oil I will use.
I just skimmed this thread; I'll re-read it more thouroughly when I can find the time.

Zinc dithiophosphates are use to prevent cam wear (excellent anti-scuffing properties), but other compounds such as tricresylphosphate (TCP from the old leaded-gaso days) also have that feature.

Thanks, Rusty. I'll read up on that.

So bottom line, change rotella @5000 or 6 mo? In a 5.9 diesel that is.
Wayne

5K may be a bit over conservative. The main culprit in depleting the additive package is sulfur, and with the ULSD, intervals could be extended. IIRC, Cummins recommends something like 12K/1 year for the 5.9L. But check the owners manual.

I am passing the following info onto those Barth owners that have Detroit Diesel engines.
As many of you know my first engine failed.
The mechanic installing my second engine(and owner of a bus conversion shop)suggested I not use Shell Rotella and instead use, Mobil Delvac 1300 Super 15w-40 instead.
He said check the info on the back side of other diesel oils and you will not find listed
Detroit Diesel Power Guard Specification.
I did check and found that Mobil Delvac was the only one to make that statement.
I have been using it ever since.
Why Delvac is the only one to list Detroit Diesel in the info.? I don't know.

Jim

1985 Barth Regency 35 ft
Detroit Diesel 8.2T 225hp- Allison 4 speed

The question is: Is a current spec applicable to a 30 year-old engine design...I don't know. OTOH, Delvac 1300 is one of the few oils competitive in performance with Rotella T, so nothing is risked using Delvac, IMHO.

Actually I doubt DD would have approved a multigrade back in those days. GM was new to 4-stroke cycle diesels (except for the acquired Toro-Flow) back then, and its experience with 2-stroke cycle would have lobbied against multigrades.

Rusty,

Isn't my DD 8.2 a 4-stroke??

Anyway Mobil Delvac works great in my engine and it is a later refined model with 225 Hp. My org. was only 205 Hp.


Jim

Yes. Excluding the Toro-Flow (which it acquired) and the antique Allisons (pre-WW II vintage), the 8.2L and 6.2/6.5L were the first contemporary 4-strokes under the DD banner.

225HP seems to be the top for the 8.2L. Oddly enough, the 6.5L is still in production, and with the AMG redesign and upgrades, can be had rated to 400+HP

GMs and 4 stroke diesels has varied results. I may be leaving some out, but the first was the Toro-Flow which I understand was a conversion of the gas GMC V6. By the time they made it a good engine, no one would buy it.

Next came the Olds 350. Another gas conversion and once again they made a good engine out of it, but by that time nobody wanted it.

Next was the 8.2 medium duty diesel. Not a bad engine unless pushed hard.

Next came the 6.2/6.5 light duty diesels. The 6.2 suffered from lack of a Turbo. But died at GM because it didn't really compete will against Ford & Dodge. But it alive and well in the Army HumVee and Rusty's Barth.

Then came the DuraMax. They got it right this time or should I say Isuzu did.

And there is the heavy duty Series 60 which was purchased by Penske when he owned DD. Not sure where this engine started life, but heard rumors that it was John Deere. Great engine, but not invented at GM.

The 2-stokes came in 53, 71, 92 and 149 cubic inches per cylinder and in almost any number of cylinders. Example, the 71 series was available with 1, 2, 3, 4, 6, 8, 12 and 16 cylinders. There are still 10s of thousands of these engines still in use.

The recommended oil for the 2 strokes was 40W straight weight due to the shearing effect (?) of the twin stroke.

As far as brand of oil, give me Shell. Used it in my airplane and all my diesel MHs. Our 8V-71 powered bus and the 8V92TA powered Newell used Rotella T 40W and the Barth Cummins uses Rotella T 15W-40. GM seems to have some type of tie in with Mobil.