Packard Forum Index » Modification Discussion

More oVomit from Mike who is often gratuitously nasty

Quote:

If you coat one screwdriver with synthetic and another with regular oil and leave them on the bench for a week the one with synthetic will have a better film on it.

I was buying synthetic for my modern car at WalMart because it was on sale for less than regular oil at NAPA. But would this make much of a difference in a slow turning Packard? Well, I knew a Mobil oil executive who changed all his Packards to synthetic. Do I get better gas mileage on synthetic? I don't think so. With a Packard I would be more concerned about cleaning the oil pan, having the optional heavy duty air cleaner, and good ignition than synthetic oil.

But if you really want to be the expert, put your car on a dyno. If the rear wheel horsepower at 50mph is higher then you can tell everybody what's what so far as oil is concerned. Do I like running diesel oil in Packards? Not particularly because those long connecting rods benefit from thinner oil coming through the squirt holes. However, Packard authorized heavier oil to reduce consumption so there is nothing in the literature that says heavier oil will hurt the Packard motor. However, on the V-12 I have seen cavitation corrosion on oil pump gears in cars running 20w-50. They weren't original gears however.

If you run any motor with less viscosity at the same temperature, you'll gain from less lost work/viscous friction(drag), regardless of it's source.
SAE Viscosity is measured @ different temperatures and why the numbers are different. A straight grade has a different curve than a multi-viscosity, 5-30, 10-40, etc.. 20-50 acts like 20W at the low measured temperature and like 50W at the higher, so it's not necessarily higher than 30, until the temperature raises. Weights are old traditional units and aren't necessarily indicative of large viscosity differences. The temperature effect is much more pronounced.
The additives modify the viscosity and film forming properties. (how they get multi visc.) These are depicted in the SAE letter designated service codes, on the can. Film has a relation to internal clearances, bearing materials, etc.
Detergents emulsify contaminates that result from combustion and thermal degradation, so they stay in the oil, so they can be discharged during changing. Without, they accumulate in the motor and oil. If you have no filter, use ND, better change oil frequently and/or be prepared to do pan cleanings. You can get problems running detergents in an old gunked up motor just as much as you can get a clean one gunked up from running ND - over a long time. It's depends how much.
It depends on what additives are in there and what motor's made out of, tolerances, dynamic balance, etc. if wear will be impacted.
Then you have the effect of the oil and additives on the non-metal parts to be concerned with. If you rebuilt with modern seal materials, you should be Ok to use modern oils. If the seals are petrified, it won't matter what oil you use, you'll get blue smoke and leakages. If you use the wrong fluids/oils, it'll attack the seal materials. I see references to adding ATF, etc. to cylinders to unstick, but that swells most rubbers. They used to sell it as an additive, so it can make an old seal pliable, but too much and seal's mush.
Diesels are another animal, the pistons are tin-plated, etc. Much higher operating temperatures / pressures / speeds / contaminates, etc. So no valid comparison to gasoline motor wear, etc.

If synthetic oil reduces friction and wear it should be especially advantageous in a long stroke engine. They are known to be at a disadvantage at today's higher road speeds because of higher piston speeds and greater load on the rod bearings than a short stroke engine. Synthetic oil should help such an engine more than a modern engine in terms of increased power, smoother cooler running and long life.

The down side seems to be synthetic's ability to creep past seals and gaskets. Possibly a newly rebuilt engine with modern seals and gaskets would be ok.

Thanks for the info Rusty. Two questions for you do they make a modern (non rope) seal for the L8s I remember a few years ago a company was producing a "new" rope seal that was I think graphite impregnated, It looked like dark grey nylon rope to me but I don't remember the details, and another company was making a neoprene retrofit system for vintage engines but again I don't think one was produced for the L8. Second question is what is the operating RPM of these things I'm guessing wide open is around 4000 RPM?

I think the problem with old rope rear main seals and detergent oil is that it washes the accumulated sludge out causing it to leak. This is exascerbated by blowby in worn motors. I used to see the same thing with hot rodded diesel trucks. Even though they had a modern seal they would leak from blow by.

The original, graphited rope-type seal, installed properly and in an engine in good condition, should give good performance for at least the life of the engine.

Thanks for the info. All of the rope seal engines I have worked on in the past all used conventional oil and I never knew how it would affect them.

There's the purists, the modernists, and the tweeners.
If I was restoring to orig., I'd use ND/what it calls for.
If I was rebuilding, do the machine work to put modern seal/bearing materials in or go resto mod/replace with modern engine.
If U R in between, expect/prepare for problems/issues...or depend on luck