docmirror

Lower content of ZDDP is a concern mostly for break-in, and later for flat tappet engines(like 928) that tend to suffer from cam wear. I am using Castrol HD 40 for my break in specifically because it has an extremely high concentration of ZDDP additive, it has a better thermal coefficient(extracts heat better), and because I'm breaking the engine in in TX in July and August. It is not an approved oil for the 928 engine. don't try this at home, and YMMV.

Once break in is done, I'll switch to one of the multi-vis oils with a high level of ZDDP. I think Castrol is still ok, but have to check again.

rjm65

I read that as, any multigrade oils such as 15W50 or 20W50 are approved when them meet SD or SE classifications.

Hilton

See the first sentence of my previous post. I'm not slamming all 5W40 oils.

Apologies to others for any collateral thread damage. This will be my last post on this topic - I dislike thread hijacking by other forum members who shall remain nameless, and would rather not perpetrate the same crime any further.

There is a key underlying assumption by the latest "approved oil" lists that the oil requirements of the M28 engine are analogous to those of the M96 flat-6. If Porsche publish a dedicated 928 list of approved oils based on actual factory testing of M28 engines, then I'd trust it. However, lets face it, they're not going to, so instead they pretend that oiling requirements, design parameters, materials and tolerances between two very different engines are similar.

I'm also not saying that generally 20W50 is superior. I'm saying that the API standards as applied to oils of higher weights permit more suitable levels of anti-wear additives, specifically phosphorous, one of the key components of ZDDP. 20W50 is just a weight of oil that suits the temperature range of warm climates well in a high-mileage 928 by providing enough pressure at startup, albeit at the cost of reduced flow. Flow on its own is not good, the pressure differential between bearing and journal interfaces is also what prevents metal to metal contact.

If you really want to read a long history of 928 oil debate, go sign up for the Landshark yahoo group and read some of its 10 year history. Lots of info there. Do a search on google for the importance of ZDDP too while you're at it.

The M96 engine is seeing a number of other modes of failure not just related to the rear main seal (RMS) problem. They're just taking longer to surface as the annual mileages imposed on Porsche's by owners aren't typically that high, especially outside Europe. For more on this I suggest you go search and read the Porsche forum at www.pistonheads.com (UK based) - some significant statistical analyses of M96 failures and engine replacements have been presented.

Research and google are your friends - I wasn't meaning to make a personal assault on your own choice of oil.

The original suggestion was just a simple means to test whether the poor oil pressure exhibited by Mike's new car is a result of mileage-related engine wear, or a more fundamental physical failure such as a warped plastic journal plug, failed oil-return, of worn bearings (OMG we're heading back on topic!!). If the 20W50 showed poor pressure, he'd need to go deeper into the heads/block with his refresh to make the car a reliable long-term daily driver.

Using a cheap 20W50 would mean the cost in chucking it away when he changes to a decent oil of his choosing for his climate isn't high.

chaadster

What I responded to was your suggestion that, based on the low oil pressure observation, that it sounded like 5W40 was in it. That was hokum.

BTW, check the ZDDP level on the 5W40 Mobil 1 Turbo Diesel Truck formulation I use:

http://www.mobil.com/USA-English/Mot...duct_Guide.pdf

White Lightnin'

Actually, the topic was BB79's $3950 '89 S4 that was for sale. The thread took many ups and downs away from, and back to, and away from the actual topic. Many insults and insinuations were thrown around about the car and the seller.

Well, the car is sold. BB79 should close this thread.

We could have new threads... like "Mike's myriad adventures with his recent '89 S4 acquisition", and "What is the best oil to run in a 928 engine -versus any other P-engine that runs at a different temperature; has different RPM maps; and different cooling methods", etc.

I would look forward to that first one.... not so much the second.

86'928S MeteorGrey

OK.

See:

"Mike's new 89 problems... " thread.

linderpat

oh ****.