jsmirand

Thank you for sharing your analysis - I don't expect changing the oil more frequently then Porsche's recommendations is harmful to the car, but at the same time, I struggle to see a connection between doing that and reduced maintenance costs down the road.

For 997/996 boards, we can read hundreds of posts on failed MAFs, window regulators, ignition switches, minor oil leaks, leaky coolant reservoirs, a hole in the radiator, failed radio, etc, but I can't recall a post where an engine rebuild/major service was brought on early because someone stuck to, and did not exceed, the manufacturer's oil change recommendations.

But maybe the goal isn't to reduce longterm engine maintenance costs, maybe the OP's goal is to be satisfied that he keeps his engine in as perfect a condition as he can, and this makes him enjoy the car more - in that case, the goal is being met.

boolala

AFAIK the catastrophic engine failures on the 997 have largely been the result of IMS issues which are not oil related. RMS failures, again not oil related. Typically what goes wrong in these cars are the electronic compenents i.e., absolutely nothing related to the frequency of oil changes.

Granted there are all sorts of people on this board who are smarter than the Porsche engineers (they told us so themselves) so who are we to question them?

Macster

Engine clearances are not fixed. While statically the clearance a main bearing has between itself and its journal may be between 0.001" to 0.0005" under operation this can vary as the crank whips a bit. There can even zero clearance as anyone who has torn down an engine can confirm due to the very clear evidence of metal to metal contact by the journal and the bearing.

Then one must consider the cam lobe and valve lift bucket. The only clearance this interface has is the thickness of the film of oil that manages to develop between the lobe and the bucket face. At this interface pressures can approach 170,000psi (and higher for other engines with heavier valve springs). The oil film is not exceptionally thick on a good day.

The oil film at the upper end of the cylinder between the rings and the cylinder wall varies considerably too. And the oil film that must exist between the piston ring groove walls and the sides of the ring.

And God only knows what oil film thickness exists in the zero lash hardware and the VarioCam Plus oil operated pins that lock the two camshaft followers together or unlock them.

Then there is the oil film thickness between the chain rollers and the chain sprocket, the oil film thickness between the rollers and the inner pin, and lest we not forget the zero thick oil film between the bearing ***** of the IMS bearing the the bearing races.

Lastly we have an oil pump that has to pump this oil, over 60 liters of it per minute, and the oil pump gets the oil before it is filtered. Over the life of the engine the oil pump could pump nearly 36,000,000 liters of oil.

Sincerely,

Macster.

mulepacker

Thanks for sharing the interesting data. At what point do you plan to change the oil again? I hope you analyze the oil from you next oil change for comparison and post the results. I would anticipate much more normal levels of contaminants which will support that the cost of the oil change is well worth the expense. It's intuitive to believe that it's helpful to get rid of the assembly debris as soon as possible. How much does the analysis cost? $20? Thanks again.

Bob Rouleau

Lala - Oil change intervals vary with use. People who track their cars change the oil more frequently than Porsche specifies in the manual.

Consider, the manual for a cup car using a nearly identical engine calls for oil changes much more frequently, in fact a Cup car used for racing is supposed to have the engine rebuilt every 40 hours (996 Cup). A 996 GT3 using the same engine has a 4 year 50,000 mile warranty. Does this suggest that perhaps track use stresses the engine and its lubricants more than a cruise on the highway?

Sustained operation at high revs is normal on track and virtually impossible on the street. All manufacturers recommend more frequent oil changes based on severe service. I suggest you inform yourself of change intervals suggested by those same engineers for cars used for racing. Cars used for both street and track should use change intervals between the two extremes which is what those of us who own and drive these cars do. What do you drive?

Regards,

Tbred911

do you not get a blood test every 6 months for preventative maintenance?

....magnetic drain plug and oil analysis is exactly that.... and I think blackstone has enough experience in the game to tell us what the threshold values are.... but that's a good point you may want to contact them directly concerning this... however... if you don't analyze your oil... your playing in the dark...

CarGuy21

BTW the magnetic oil plug is only good for ferrous based metals i.e. iron, steel, etc. not aluminum, copper, brass, lead, nickel, etc. The point being that you could develop a false sense of security if you depend upon the presence or absence of material on the plug as an indicator of engine health.

These engines have cylinder sleeves so they're not like the old Vega engines where the pistons are running in aluminum cylinders. The crankshafts are either cast iron or forged steel (I don't know which) so the only sources of ferrous metals are the cylinder sleeves, crankshaft, camshafts and oil pump.

Tbred911

that's a great point!... I know during the first 1,500 km break in there was lots of metalic dust around magnet plug .... but the whole point here is to send the oil away for stuff that doesn't collect.... I rely more on the oil analysis than the drain plug... the drag plug is only there to pick up chunks... if you've got a chunk attached you know something is going down... lol...

Fahrer

Actually the 997 engines do not have sleeves ( unless they were repaired). The cylinders are aluminum with Nikosil(?) ( for the 997.2) or Lokasil coating on the aluminum cylinder surfaces ( for the 997.1). Both have proved to be durable. I think the Vega invloved a number of design fiascos.

LlBr

FWIW, Porsche allows a huge amount of variation in oil consumption from engine to engine. Up to 1.6 qts per 622 miles!!!? What does that mean? I don't know but maybe it's safe to bet that every NEW engine is different as far as clearances (and quality and longevity?) are concerned. So there may not really be a standard from which to judge a 95% good brand new engine from a 75% good brand new engine: both will wind up in cars at factory.

CarGuy21

Thanks!! I wasn't aware of that. Yes, the Vega had a number of design issues, etc. Not on my list of cars I've ever owned.

Clifton

FYI - some 997.2 do have steel lined cylinders (e.g. 3.8L).

Clifton

More than likely, it will be a year before the next oil change. I don't drive the GT3 that often (weekend toy) so I will struggle to get 2-3k in that time frame. I will still send the oil in for analysis and I would expect the high ppm counts to begin to level off and return to normal levels.

Blackstone's basic test is $22.50 - worth it to see the health of an engine.

Fahrer

I missed that info. Which ones have the liners?

Clifton

As stated above, the 3.8Ls, specifically the GT3s.

Porsche added steel liners because they reached the bore limit of the motor. They did so to reinforce the walls which also came with a 7.7lbs weight gain.