hacker-pschorr

So, which "racing oil" do you use and what kind of mileage / time between oil changes?

Wolfman928

Phoned the shop today to make sure on the oil used, I was mistaken, they have used Merc SAE 5w40 - 299.5

anyway, thanks for the input guys,

rgds
J

SeanR

Are you going to get it changed?

davek9

Eric as you know I do not Race my 928's, some do see the track on DE days with local PCA, the Mobil 1 20 w/50 with a splash of additive does just fine, if I were to actually race a 928, it would be a heaver grade well into the 60w's or higher (actual racing grade oils).

The only reason I mentioned "Racing" oils, is that most Auto supply stores sell so-called "Racing Oils" that do contain the proper ZDDP/Zinc levels a Flat Tappet engine requires and would not require a ZDDP/Zinc Booster for avg street driving.

As for Oil change intervals, once every 10 years or 60k miles, same as the T-Belt service

hacker-pschorr

In most oil threads we tend to talk about absolutes, not generic maybe's at auto parts stores. Locally I sometimes see Brad Penn which has "racing oil" on some of their labels. Also Valvoline VR-1 which comes in 3 flavors and only one is a true racing oil I wouldn't use on the street (even though they all say "racing" on the label).

Those two aside since they have been vetted to have the old levels, any other generic house brand that just says "racing" I wouldn't assume has 1100/1200 ppm of ZDDP unless it says so on the label or you've found independent testing to verify it.

NAPA carries Royal Purple, but I've never seen their racing line XPR on the shelf, only the street sauce HPS which is also known to have the minimal levels we look for.

Wolfman928

Nope, I doubt it, I drive around 1500-2000 miles per year, I also believe modern oils has better lubrication properties than ZDDP oils from the 1970's

dr bob

Bottom line will be the ability to maintain hot oil pressure with engine idling. The first number in the oil is the cold viscosity, second is the hot film strength. Contrary to popular myth, the oil doesn't actually get thicker as it gets hotter. The 5W number, in our colective experience, isn't enough to maintain the minimum 2 - 2.5 bar hot oil pressure needed in the 928 to maintain flow through all the lubricated systems. Like the crankshaft bearings. Go ahead and try the oil you have put in there, but keep a close eye on hot idle oil pressure. If you see it drop below 2 bar, swap the correct oil in there. All the ZDDP and high hot film strength oil does you no good if it doesn't make it to the bearings.

davek9

"... In most oil threads we tend to talk about absolutes, not generic maybe's at auto parts stores. Locally I sometimes see Brad Penn which has "racing oil" on some of their labels. Also Valvoline VR-1 which comes in 3 flavors and only one is a true racing oil I wouldn't use on the street (even though they all say "racing" on the label).

Those two aside since they have been vetted to have the old levels, any other generic house brand that just says "racing" I wouldn't assume has 1100/1200 ppm of ZDDP unless it says so on the label or you've found independent testing to verify it.

NAPA carries Royal Purple, but I've never seen their racing line XPR on the shelf, only the street sauce HPS which is also known to have the minimal levels we look for. ..."

Agreed, and the OP needs to either add a ZDDP/Zinc booster to the oil the shop used or change it to one that contains the correct additive levels for a Flatt Tappet engine that is in all year 928's.
Unless he knows exactly what the additive levels are in the oil that is in his Shark

Dave

davek9

This is so true

Wolfman928

sure thing !

if you compare for example 5w40 to 5w30 the 5w40 will be higher viscosity or 'thicker ' at high operating temps so that why I say or lots of people say the oil thickens at operating temps...anyway guys I don't want to create another 'dead rubber' oil thread..

SeanR

Ok, good luck.

FredR

You do not appear to understand the issue here. The problem is not the oil it is the mechanical design with flat tappets. Run a modern fully synthetic oil in the 928 motor without any ZDDP and the cams/tappets will likely get chewed up. There are two types of lubrication mechanism in the engine- force fed and splash lubrication and both mechanisms have to function correctly with a single oil formulation. The problem is more modern engines run with roller tappets and the loading is much less and modern oils are designed with this in mind.

The 928 cams are splash lubricated and the duty is doubtless the most arduous of all the lubricating duties in the car. That being said folks invariably say "we need 1200 ppm of ZDDP in the lube oil" but I often wonder how many really know what they are talking about as more than likely most will simply be reporting what they quite understandably have been advised is needed. When I did some research into this topic not too surprisingly the amount of ZDDP needed is functionally dependent on a number of parameters such as cam lift, valve spring pressure and where the motor is normally operated rpm wise. Thus for a racing engine that might typically have hot cams and stronger valve springs the problem may well be chronic and thus need the 1200 ppm spec whereas, on a stock 928 motor street run with say S4 cams, a ZDDP content of 1200 ppm may not be needed. The only example of 928 cam wear I have read about was on a GT cam [higher lift] but that may well have been because of inadequate ZDDP content.

Thus we know that if we use an oil with ZDDP content of 1200 ppm we are safe but whether anyone really knows the minimum safe threshold for a street driven 928 motor remains to be seen. Bottom line these engines are 70's technology and will run forever on the correct oil when changed regularly.

SeanR

Fred. The cam wear is very prevalent. Two guys at Frenzy were talking about how their cams are pitted and they knew exactly why. This is a 90 that was shipped to me and am tearing in to it this week. (Ignore the rust, the retard who worked on it before me left the covers off). Getting new cams. Replaced the cams on 2 GTSs and several s4's. Anymore if people don't want to listen on oil recommendations I just say good luck and let someone in the future make money on replacing the cams.

hacker-pschorr

None of us are running oils form the 70's. If there was a 100% replacement, no "modern" oils would contain any. But alas, they still have 600-800ppm in every oil on the market.
Don't believe me? Here is every oil from Mobil 1 listing the ZDDP levels:
https://mobiloil.com/~/media/amer/us...pecs-guide.pdf

ZDDP is still the most proven substance to cushion between camshafts and flat tappet lifters, like it or not your engine has a "design from the 70's" with that style camshaft / lifter.

Boron was considered the answer for quite a while but increased testing has shows it doesn't quite stack up:
https://www.hemmings.com/blog/2012/1...older-engines/
Manufacturers have tried adding more boron to offset the effects of the reduced zinc and phosphorus levels; however, the dry start protection does not measure up to those using more ZDDP/ZDTP.

Your other issue is ignoring the manual on oil weight. You act like none of us have every considered what you are thinking is correct. At least 6 people documented in the forums over the years the effects of using a lighter oil on hot day. We're not talking Phoenix in July, but anything in the mid to upper 80s. My personal car, on such a day experienced lower than comfortable oil pressure and lifter ticking at idle. If you car will never experience ambient temps above 70, then you'll probably be OK, maybe. Not sure what you are trying to prove by risking it.

Wolfman928

Fred and Sean I disagree, I had my engine and cams checked and it looked nothing like that, my 928 was serviced by Porsche agents the first 12 years of its life and thereafter mostly Castrol GTX and Castrol High Mileage which is 20w50 Multi grade and 10w40 Synthetic respectively, well that is all I could see from the history on the car the last 20 years or so, it has 115k miles now, it was mostly driven long distances, going away weekend/ holiday car but the car was driver regularly, no evidence of racing/ track etc, previous owner is a car collector and he makes time to drive his cars and the guy before him gave me some years of info and how he looked after the car.

it comes down to proper maintenance, regular oil changes, warming up oil before letting foot down and non standing for long periods (regular driving )
I'm not saying you are wrong on the Zinc and the effect and protection it provides etc, I just believe this is not the only thing that counts...