FredR

In the area behind the 1/4 cam sprocket

davek9

Like Stan said, you need a 20w/50 or even a 15w/50 racing type oil (especially in an Auto in Summer heat) not sure of your driving conditions.
Autos tend to run a bit hotter due to the additional heat in the Rad from the Trans cooler, thus thinning down the oil.

Most important and I didn't see mentioned here is the ZDDP level contained in the Oil type, You need an Oil that is formulated for FLAT TAPPET engines, hence the "racing oil" reference.
W/O the proper oil type, you will destroy your Cam lobs and tappet surfaces.
Consider what you did as an "oil flush" and replace it ASAP, or add a ZDDP additive, until your next oil change.

Dave K

SwayBar

None of this is even remotely true...

Please consult your 928 Workshop Manuals for recommended oil-viscosity for a given temperature range and get back to us.

And while you're at it, check for the need for a 'racing oil'.

hacker-pschorr

+1

Real racing oil (not just some with the word "racing" on the bottle) has few if any detergents. Fine for a real race engine which sees very frequent changes, bad for a street car.

As for ZDDP, we cover this a lot around here. Almost every oil had "enough" ZDDP prior to 2001 or so. That magic number is 1100/1200ppm. The EPA stepped in, found out zinc might damage catalytic converters so reduced the numbers for oils which want to carry the newest certification to 600/800ppm.
Mobil 1 scared the bajesus out of the car world when they initially dropped the ZDDP levels in their 15w-50 to the new lower levels (so did a few others). It took a few years for the dust to settle and most 15-20w/50's returned to the old standard since few (if any) new cars called for such a heavy oil so there wasn't the need to have it stamped with the latest standard to satisfy new car requirements.

One only has to find an oil with the old amount of ZDDP and most 15-20w/50's fit the bill. In fact the only one I'm aware of that doesn't is the cheapest non-synthetic Castrol in the white bottle. Every other 15-20w-50 I've been able to get numbers on were 1100/1200 or higher. No need to go overboard unless you are building an all out race motor.

Wolfman928

I do like the traditional 20w50 multi grade oil used, they used Castrol GTX 20w50 over the years and there was really no problems with that, its really a cheap or the cheapest oil available, the guys from RS Auto recommended 5w40 from Liqui Molly which does contain Zinc, where I live the climate is moderate with cold mornings especially winter time, so the 5w made sense, less engine wear (cold start ) but then yes I do agree the w50 is better for high temps, especially engines like the 928 running more hot. I was thinking about Fuchs Titan Sypersyn 5w50 also Synthetic oil to use on the next oil change, not sure about the ZDDP additive, speaking of which I was under the impression ZDDP was more a neccesity for older engines from the late 70's - maybe early 80's ? am I wrong ? its all about maintaining a strong oil film on the metal layers (liners ) on high temps...

cheers
Johnny

SeanR

Your car is an early 1970's to mid '80's engine design. Stick with a 15w/20w-50 oil and never worry again.

Wolfman928

this is really not a problem, I don't race my 928, it's more of a weekend cruiser, most recommend 10 or 15w40, yes the 5w40 might be a little on the low viscosity side but the nice thing is now after the oil change my engine sound is smooth, well more smooth now, I have no noises on cold start, this is a sign of a healthy engine with the fact that it does not smoke, I had a guy driving behind me and he says my 928 does not smoke at all !!!

hacker-pschorr

As I mentioned above, Castrol GTX 20w50 conventional / multi-grade is one of the only Xw-50 grade oils I was able to confirm does NOT have the proper levels of ZDDP. I bought 5 gallons of it off Amazon when it was on super sale and sold it to my local indy shop once I received the specifications on it from Castrol.

The issue with lower levels of ZDDP is the lifter to camshaft relationship. So unless someone was doing oil analysts and / or pulling the cam covers to check for cam pitting, you would never know if this oil was or was not causing harm.

Most of these cars receive new oil once every 12 months. 10 quart system, so an oil that costs $5 more a quart is only an extra $50 a year. Not a place to go cheap, in fact no place on a 928 is worth going cheap. It will only cost more in the long run by doing so.

All oils contain ZDDP or Zinc, it's the level of the ZDDP in the formula that matters. Adding a ZDDP booster has mixed results since the overall additive package of the oil you are using is what matters.

It all has to do with the type of lifter, the flat tappet style in the 928 is what needs the higher (old) levels of ZDDP. The 928 engine was designed in the mid-70's.......

READ THE MANUAL - 20w-50 rated OK for use with ambient temps down to 15F, 15w-50 a tad lower:

FredR

The ZDDP is very much necessary for the flat tappets/cam nose. It has little to do with oil film strength per se- albeit that is also important - rather the ZDDP plates out on the metal surfaces to create a surface finish and thus help prevent metal to metal contact- the entire point of lubrication. In case you did not notice the 928 engine was designed in the early 70's- yours is a later iteration of the same thing with 4 valves per cylinder and DOHC's.

Wolfman928

Thanks bro ! I read Porsche A40 spec on the oil I used and I believe that's suitable for Porsche engines after 1984

Wolfman928

and a larger capacity of 5,0L, how do you know the liners are the same than those from the 70's?

FredR

What liners?

The cylinders are bored into the casting material of the block- Alusil.

hacker-pschorr

The primary oil passages did not dramatically change from 1978 to 1995 with the 928 (or 944) making the oil requirements the same across all models.

Much debating on this, the A40 spec didn't really take into account the water cooled engines, and the fact that Porsche released a 10w-50 in their classics line specifically targeting the 944 / 928 tells you everything.

NoVector

That feature was added later to the GTS models. In addition to providing internal lubrication & anti-corrosive protection to the intake and exhaust, it also greatly reduces mosquito larva around stagnant waterways.

davek9

If you say so, than it MUST be true.

Also note, the manuals were written way before modern oils were developed w/o proper ZDDP levels for Flat Tappet engines, as far as viscosity goes, it's your choice then.

I'll continue to run what I've been using for 20 plus years in my 928's and 1972 Jaguars (and YES, I have taken apart my engines after many many miles and years to re seal and have found NO issues w/ CAM or tappet wear).
However, I can not say the same for the others that I've done.