Geojerry

This topic always brings about lively discussions.
So, he we go.

Zinc additive has been removed from most modern oil.
For older high performance cars as our 928, many engine
Specialist recommend adding this after an oil change.

For the past 5 Years, been using ZDDP plus ( $9 bottle) on my
Two classic cars with muscled up engines after each oil change (no synthetic).
No issues and engines still strong and lively.

For my recent acquired 91 928 S4, plan to do the same.
Not sure whether to use Mobile 1 Syn or 10w/30w down here
In Hot and humid South Fla. What's you think on the Zinc additive?

Rob Edwards

10W30 is a Bad Idea. Plenty of threads on this, just search with the key words ZDDP and ppm, and youll find the right threads. Would do it for you but am on this stupid phone....

hacker-pschorr

Oh boy, an oil thread

That depends greatly on weight.

The new modern standard with lower ZDDP is targeted towards the lighter weight oils in most modern cars.
This does not apply to the 928.

I have not found any 15-20w/50 oils that are lower than 1100ppm ZDDP - which is the "old" standard our cars were built around.

Even Mobil 1:
http://www.mobiloil.com/usa-english/...duct_guide.pdf

If you drive your 928 in a cold climate that would call for 5w-40, there are options like Mobil 1 Turbo Diesel Truck, Redline, Amsoil etc......


Quite a few non-synthetic oils still have higher ZDDP standards since they are not produced for or marketed towards new car owners. You simply need to look at the bottle.

Every oil with GF-4/GF-5 in the bottle will be 800ppm ZDDP which is the new "environmental friendly" amount, and not what you want.

The issue of low ZDDP levels is 100% related to camshaft wear in engines with flat tappet lifters (like the 928).

Andy Kay

I've been using Valvoline VR-1 Racing Oil 20W-50 in my 79 911SC for the high level of ZDDP. The 87 928 gets Mobil 1 15W-50. Never been a fan of oil additives.

GregBBRD

1. 20/50 Kendall (non-synthetic) (used to be common in Florida.) Continue to use the Torco oil additive.

2. 15/50 Mobil 1 (synthetic) and continue to use the Torco oil additve.

3. 20-50 Torco TR-1 non-synthetic and no additive. (My personal favorite.)

4. 20-50 Torco SR-1 synthetic and no additive.

5. Brad Penn 20-50 and no additive.

DO NOT use 10/30. These engines were not built with these thin oils, in mind!

ROG100

Some common sense thoughts from a very well known 928 expert from down under.

Last century Porsche engines very much need high oil film strength engine oils if one wants as much long life as possible out of items that have no oil pressure keeping the metal parts away from each other , such as }

A ) valve guides ( air cooled 911 huge wear issue )
B ) Cam lobes & hydraulic lifter faces ( flat tappet design )= 944 / 928
C) Crankshaft thrust bearings
D) Camshaft chain sprockets ( 944 & 928 twin cam heads)
E) Alloy piston skirts against alloy cylinders
F) 911 air cooled rocker arms contact faces with cam lobes

All the above we have seen exceptional wear , meaning high wear , when these engines have been on low viscosity so called synthetic engine oils , and conversely we have little or no wear on the same types( & 3 times the milage) where they have been on the oil viscosities recommended by Porsche that is printed in the owners manual that came with the car new .

So on a last century Porsche }

911 air cooled ( all year types )
924
931
944
944S
944S2
928 ( 4.5L , 4.7L, 5.0L , 5.4L )
968
951

We see in the owners manual on the oil viscosity page , the oil chart showing ambient temp ranges

In the "Look at me " shaded section of this page under the heading of multi grade oils we see the first ambient temp range of = minus 10 deg cel to unlimited high ambient temp ( sounds like Australia to me ) , we then see the recommendation of a 20w-50 & 15w-50 ,
One does not see 5w-40 etc in this temp range

Note } in Porsche cars ( 928 , 911 , 944 etc ) up to about 1983 or so the ambient temp range for a 20w-50 was minus 15 deg cel to unlimited high temp range

Now lets go to engine oil film strength }

Question = how do I increase oil film strength with an engine oil on this planet in this universe ?

Answer = there are two basic ways

1) increase the oil viscosity ( say from a 5w-40 to a 20w-50) if both oils have the same amount of ZDDP

2) increase ZDDP or add Molybdenum ( in conjunction with ZDDP ),which enhances the effectiveness & life of the ZDDP

So if you add the two ( meaning 20w-50 & ZDDP ) = high oil film strength

Subnote } most if not all 20w-50 engine oils are OK in respect to their ZDDP amounts , because last century engine's & oils are not subject to this century emission protocols , most cars in this century use much lower viscosites ( engines designed for this)& to meet the emission protocols( lower levels of ZDDP & no Moly), meaning 0w-30 , 0w-40 , 5w-40 oils for this century cars are generally lower in their oil film strengths as compared to a 20w-50 with ZDDP , even though the replacement AW ( anti wear additive) of ZDDP ( read Boron ) has not been as useful in regards to increasing oil film strength as ZDDP was / is in last century viscosities.

There was even one famous oil company here in Australia that experimented with dropping the amount of ZDDP in their 15w-50 just over a decade ago & that was interesting , we saw quite a few worn cams and above parts mentioned above within 60,000Kms( on average) , Oh and by the way the same oil reverted back to a higher ZDDP ( it can be a bit of a mine field at times)

So you can see why I am not easy about recommending even a 15w-50 , even though it was probably a one off

The reason we can figure that easily is one only has to look at the advertising for this century racing oils for "this" century engines & oil companies are falling over each other to show how much ZDDP is in their racing oils , and yes they are not falling over each other to show how much more Boron or any other AW additive they have added , they just go on about ZDDP , so it must work over wise they would just say things like " we have added twice the amount of non ZDDP AW replacement like Boron etc " , well this is not happening , its ZDDP , yep last century solutions in this century racing oils ( who would have guessed that )

Now lets go to primary diesel engine oils , like Delvac etc , excellent oil for a diesel engine that is designed for that viscosity , however Mobil & Porsche do not recommend a diesel oil in a petrol powered engine , not last century & not in this century

Now why is that so ?
Answer = primary diesel oils are very high in detergents( compared to petrol powered oils) and these detergent packages tend to make engine oil foam too easily , so they then add silicon to reduce this tendency , but detergents attack the ZDDP , thats why primary diesel oils look as if they have very high ZDDP( new) , but as time goes by the ZDDP is damaged by the detergent packages .

Now back to the foaming , if a petrol engine from last century revs harder to make its max power as opposed to a diesel engine from last century ( like for like) this in quite normal , so in a big rig that cruises on the freeway at 1,800 RPM will give the oil way less tendency to foam as say a sports car / GT engine that is being revved to 6,500 RPM a lot .

This is where it gets interesting , foaming / air bubbles in the oil is the VERY last thing you need in a 944 / 951 or a 928 , because they have a very small flaw in their crank oil feed design , they starve no 2 con rod bearing ( 944 / 951 / 968 ) and 2& 6 con rod bearings on a 928 if the oil pressure drops to low.

How do we drop the oil pressure with a high core temp ?
Answer = use a 5w-40 oil ( in Australia) , then make it a diesel engine oil that will foam more easily & you are putting the bottom end at risk for not net gain what so ever

How do we reduce / eliminate this from happening ?
Answer = we consult the owners manual ( very easy stuff to understand)

Question = Do we see people destroy last century Porsche engines at the track when they are running even slightly lower viscosities ?

Answer = used to be very common , now getting better as people get better educated by reading their owners manual

Question = How do we eliminate this human tendency of wanting to use this century oils in last century Porsche engines .
Answer = Education .

Now onto oil pressure for a bit , we used to get ( every summer ) 928 ( all types) 944 / 951/968 turn up at our workshop with their oil pressure warning light glowing brightly at idle , naturally its a hot day & they have spent a few hours crawling in heavy traffic to get this high core temp ( no not coolant temp ) I mean core oil temp , and this is normally due to 5w-40 , we even get the odd one do it on a 10w-40 , so for these conditions the only thing that works is a 20w-50 ( never fails ( so long as the engine is not already badly damage by running around with a low vis oil

Remember , if the oil warning light is on at idle , then you can not go for full power because the con rod bearings are at severe risk at high revs , on a 20w-50 this will not occur .

Regards
Bruce Buchanan
Buchanan Automotive

GregBBRD

Well said.

antlee928

+1. BB does know his oils and as Castrol used to say in their advertising here in the 70s/80s that "..oils ain't oils...)

Cheers

antlee928

The answer is right in front of us. All we have to do is RTFM ;-)

Cheers

brealytrent

Funny, my 924 takes 10w/30 and the manual says it's okay for the oil pressure light to come on at idle from time to time :P

jeff spahn

I used 10w-30 when it was super cold, like -20's F. The 20w-50 hard a very hard time turning over after sitting outside. Switched it to 20w-50 as soon as it started to get above the 40's or so.

NoVector

When talking about Torco engine additive, you're talking about this one with ZEP, right?
If it is, where do you normally buy it? Getting my shopping list together for my next trip back to the States

ROG100

I know Greg Brown has the Torco addative.
Maybe need to stock it as well as the Swepco

Leon Speed

hmmm

antlee928