Finally decided to go with 20W50.

[Maleficio]

Originally Posted by Dean_Fuller

I know some will disagree ( oil additive to some are a no no ) but try some RESTORE...its formulated to help keep oil up in the higher areas and not settle in the pan. Although the label doesn't say I would think it has zinc in it as its been around awhile now. I've used it in other cars I've had with high miles and it really did help the engine smoothness.

Maleficio...where do you live?

I'm in middle TN.

I tried Restore once. It made a difference. I could tell I had improved compression. The effect lasted about two weeks.

[waynestrutt]

Porsche recommends multigrade oils in all the owners manuals. Definitely flow is important hence the pump but viscosity is vital or we could just use high flow water.All multigrades are never thicker than the lowest number even when hot so your choices for cold starting is either 5 to 20 weight. The important number is the second number that the oil maintains that of its comparable viscosity when hot.

(excerpt)

[ For all year round filling (oil change intervals 15.000 miles/24.000 km) use multi-grade oils
SAE 10 W-40, SAE 15 W-50 or 20 W-50. The 20 W-50 oil should not be used at constant
temperatures below + 5° F/-150 C.
Porsche recommends the use of single-grade oils only if multi-grade oils are not readily
available. Oil changes must then be performed according to season to guard against engine
damage. The following viscosity can be used: in summer SAE 30, in winter SAE 20 W (only
at constant temperatures below + 41° FI + 5° C).
Porsche does not recommend the use of oil additives.


E n g i n e Oils — petroleum based and/or synthetic based Always use quality oil labeled "API Service SF or SE" which has been approved by Porsche.
The terms SF or SE may appear on the oil container singly or in combination with other designations, for example: SE/CC, SF/CC or SF/CD. Engine oils are graded according to their viscosities.
The grade to be used depends on existing or anticipated seasonal climates. Refer to the
temperature chart when selecting engine oil. If you need to add oil, it is permissible to mix oil of different viscosities. As the temperature ranges for different oil grades overlap, brief utside
temperature variations are no cause for alarm. When using SAE 10 or SAE 5 W-20 engine oil.
avoid high speed long distance driving if outside temperature rises above the indicated limits.
Single grade oil
Porsche recommends the use of single grade oils only if multi grade oils are not readily available. However, engine oil changes must then be performed according to seasonal temperature changes to guard against engine damage.
Multi grade oil
For all year round driving use multi grade oil. Oil change intervals specified in the Warranty &
Maintenance brochure accompanying the vehicle must be adhered to, including intervals
for oil filter change.
Fuel-efficient-oil
For all year round driving a top quality "Fuel-efficient"- oil can have a beneficial influence on fuel economy. Before selecting these unconventional oils, consult your Porsche dealer. ]


see page 102 in the 84 owners manual .Not all the manuals have the chart.
Owner's Manual - Online - Rennlist Discussion Forums

[Plexus928]

On older higher mileage engines, it pays to avoid oils with a high detergent content,(Always check label) These keep new engines clean, but as I found out years ago when I started using it in a Jaguar motor, it was the sludge that was sealing the rings, a couple of days on the high detergent oil, (Went through faster than sh.... through a duck,)cleaned the rings so good it was impossible to see out the back window through the smoke.

[Pete R]

Originally Posted by waynestrutt

Porsche recommends multi grade oils in all the owners manuals. Definitely flow is important hence the pump but viscosity is vital or we could just use high flow water.All multi grades are never thicker than the lowest number even when hot so your choices for cold starting is either 5 to 20 weight.

We could use high flow water. It's not the viscosity of water that doesn't allow it to be used it's the fact that it turns to steam at operating temps. Water lubricated bearings are ofter used in marine applications of things like prop shafts. Have you ever seen hot 5-20? Pretty close to water.

To say that it never gets thicker than the lowest number is wrong. The viscosity test is temp dependent. So if its colder than the testing temperature, it's thicker. That's why climate is important.

[waynestrutt]

Pete
We are talking about real world applications (where we drive our 928s)
If the oil is continuously overheated yes it will thicken as the lightends are driven off
( evaporated).But the temperature at which the low number is given is for approx -20 F or about -30C. At these temperatures I recommend your favorite chair , Jack Daniels and a roaring fire.

[lukerman]

Not sure if this is applicable but I drove several ford rangers when I was growing up and I ran it hard, and I always ran 20w 50 in it, and even in st louis winters, they survived. I always had lifter noise if I ran the 10w 30 or 40 and the 20w 50 fixed the problem. I feel the harder you run anything, thicker oil cannot hurt. for what its worth, thats my 2 cents. the same goes for my 71 mustang.

[Pete R]

Originally Posted by waynestrutt

Pete
.But the temperature at which the low number is given is for approx -20 F or about -30C. At these temperatures I recommend your favorite chair , Jack Daniels and a roaring fire.

Ha, I agree.. but you know there's some crazy dude in Canada that's dd his 928 at -20, there always is

[waynestrutt]

It was -7c here Sunday and the 84S I bought Saturday for 800.00 and struggled to winch it onto the trailer and off into my shop fired right up with a new battery. I bought it for parts because of the corrosion and worn interior but am now considering restoring after I finish my 80.The 84S sat for a couple of years with no attention. Po bills indicated new exhaust brakes and oil and filter with 20-50 used

[Maleficio]

Modern oils are nothing like they were thirty years ago.

[Danglerb]

Just a wild guess, but 90% of the information I've seen by individuals about oil details are wrong, often fundamentally and conceptually wrong as well as misguided, wrong headed, and factually flawed.

OTOH I am willing to accept that at least 10% of my own knowledge is faulty, so I have no idea what is correct. I have learned that running without oil is bad, especially with hydraulic lifters, but not much beyond that.

My first car had a LOT of miles, and would knock when cold with anything less than 80 wt oil. It also had a weak generator that took 6 months to get from Italy, so when cold it would either start on the first rotation or not at all. Once the oil got up to about 185F it started to feel pretty frisky.

[Maleficio]

Originally Posted by Danglerb

Just a wild guess, but 90% of the information I've seen by individuals about oil details are wrong, often fundamentally and conceptually wrong as well as misguided, wrong headed, and factually flawed.

OTOH I am willing to accept that at least 10% of my own knowledge is faulty, so I have no idea what is correct. I have learned that running without oil is bad, especially with hydraulic lifters, but not much beyond that.

My first car had a LOT of miles, and would knock when cold with anything less than 80 wt oil. It also had a weak generator that took 6 months to get from Italy, so when cold it would either start on the first rotation or not at all. Once the oil got up to about 185F it started to feel pretty frisky.

80 weight?

Is that gear oil?

[Danglerb]

Valvoline 80wt racing oil. Alfa Romeo dohc 1600, ran great once started, greater once hot, but wouldn't stay hot unless it was driven hard. Normal driving dropped down to about 165F. Its the car I learned to drive sideways in thanks to the linked arm rear suspension.

[Pete R]

I have read extensively about oil, oil testing, oil additives, cold oil, hot oil, hot oiled babes, everything about oil. and you know what, I'm still using the same oil as before. The simple fact is it really doesn't matter. I've read about race guys filling their cars with 2 stoke oil so when it gets into the combustion chamber it burns and doesn't detonate. Most of us have well over 100k on all our motor. We're using walmart oil to amsoil. I don't remember ever reading about an oil related failure. (maybe lack off). If we were racing and running at 5k rpm + all day I'd worry, but since we had a 2 page thread on cupholders that doesn't seem to be the case. Don't worry, just make sure there's some in it and change it every now and then.

[Maleficio]

I hear ya, Pete. I used to be an Amsoil dealer. But I never fully grasped the ins and outs of viscosity, etc.

Whatever the case, I'm sticking with 20w50 in the 928.

[milkman383]

I hear ya Pete, I've done lots of research and dealt with lots of people who had religious convictions about motor oil. I maintain a handful of racecars for people and seen every sort of failure you can imagine. If I had to boil all this down to a few things that people should keep in mind it would be simply -- thin oil isn't good for racing (or really high rpm driving), if you change your oil often enough it doesn't really matter what you run (unless it's too thin), if you think an oil is the best thing ever, then use it, change it often enough and don't run anything too thin and you'll be fine. I've got a chassis dyno and these claims that a given oil makes HP are hogwash, if the oil is at the same temp and was the same viscosity I've never found a difference. Yes, thicker oil costs a few HP, but if the motor lasts longer who cares? Oh and it's better to run a little too much oil than not enough. (Except in a dry sump) Oh and another cool fact. Mobil 1 would be clear if they didn't add color to it! Ok, that's what I've figured out about oil.

[dcrasta]

My 2 cents..

Use the thickest viscosity oil you can get away with (within reason) .. This would generally be the 20w50 Multigrade oils. Viscosity helps oil cling to things. Thin oils run faster. This is good in some motors (like air/oiled cooled motors) where you want the oil circulating as fast as possible. I could see an advantage to lighter oils in cars like ours, (faster draining back to the sump) however 20w50 once its at operating temperature flows very well. And it is recommended in most climates.

In any case, use the recommended viscosity for your climate and change frequently and you can rest easy.

[Sapientoni]

Porsche has pressure reliefs built into all their oiling systems. At track events you always do a warm up lap to thin the oil out. 2.5 bar at idle is normal when warmed up, 5 bar at 2500 rpms after warm up, right guys? Smokey Yunick said you need 10 psi for every 1,000 rpm, so Porsche thinks more is better, and they're pretty much correct.
I remember reading in the 60's that Ferrari racing teams had to "tickle" their engines to life and couldn't rev them much when cold or they'd pop an oil cooler. Hadn't invented the bypass thermo valve yet.

[Danglerb]

A lot of what is "best" depends on the bearings and how the engine was designed. Newer engines have different tolerances than our old 80's design.

When a bearing gets too hot it fails, oil flow does the cooling.
Too hot is the temperature where the oil actually starts to fail, not the bearing itself.
Thin oil may flow through the motor too well, so some parts of the motor lack the pressure to overcome the forces created by the movement of the parts like the crank, and starve some bearings.
Thick oil may not flow through the motor well enough, and starve some bearings.
Oil needs to match the motor design.

I don't know how much viscosity and film strength are related.

I don't think pressure at a bearing matters much if at all, just flow. I'm pretty sure a zero pressure oil source with a vacuum on the crankcase to pull the oil through the bearing would work fine as long as the bearing tolerance was sufficient for the flow and the rotational forces didn't effect it (no tying the feed to a rod bearing).

[waynestrutt]

[QUOTE=Danglerb;6444735]
I don't think QUOTE]

Even with a vacuum you still will have atmospheric pressure 14.7 psi or 1 bar.
Valvoline 80wt (racing oil? actuallygear oil ) has a viscosity just above todays 10w.

Here is an interesting article.

All About Motor Oil

[Maleficio]

Great article.

I like this part:

‎"Most oil wells throw off a lot of natural gas. In many cases, it's more expensive to transport this gas to a large city than the gas is worth, so it's just burned off. For example, Iran burns off enough natural gas each day to power their entire country, electricity, cars, ships, airplanes, the whole thing. So the next time you hear Iran's nuclear reactors are purely for peaceful production of energy, you can wonder like the rest of us why a country that burns off more than their entire energy needs must spend tens of billions of dollars developing alternative energy sources."