OVRSTR

Just checked my owners manual for oil service intervals for the S. It stated that under normal operating conditions, the oil service interval is every 20k miles...at least I think that's what it said. Is this correct? I realize people have their own opinions on the frequency of oil changes so I'm just trying to interpret the factories direction on this. Is it in fact every 20k? Thanks everyone and God bless Mobil 1!

Jeffrey Behr

Indeed it is. I change mine about every 10K-miles.

ltc

I just can't get myself to go longer than 7500 miles without changing the oil and filter. 15K miles now 2nd and oil/filter change is scheduled for next week.

Doug Hillary

Hi,

if you check in the 928 Forum you will see testimony to Porsche's recommended oil change intervals

Check under "Oil Condition Reports", there are six Used Oil Analysis results taken over 18 months using two different oil viscosities. The reports are from a Laboratory specialising in oil analysis

It may indeed be counter productive from an engine wear viewpoint to change the engine's oil sooner than recommended. Some continuing research from the University of Michigan is showing that greater engine wear occurs in the first 3k after an oil change. There are many technical and chemistry reasons why this appears to be so.

The research continues!

Regards

ljugete

Would you recommend changing the oil & Filter once a year if you don't drive it for 20K miles a year - like it's recommended for the 911?

Torags

You've got to allow the engine to break in. The first fill gets very black very early. Thats more a condition of the aluminum (turns black) particles. It also affects the oil viscosity (gets thicker & probably undermines the oils' ability to respond to temp change).

While an analysis may find a large content of this in the oil; these particles may help break in the engine.

If you have ever wet sanded a car finish, the paint dust help buffer the grit in the sandpaper, giving a better polished surface.

Doug Hillary

Hi,

ljugete - I would suggest an annual oil change even if the distance has not been covered. The change should be in the spring!

Torags - In my experience it is important to leave the initial fill in the engine for the period recommended by Porsche. The factory fill oil is a very special formulation designed to assist the engine break in process
Break in can continue for 30k or more and will be slowed if a high quality oil is installed prior to the end of the period recommended for the factory fill to remain in the engine. This may lead to bore glazing and or etc. and high oil consumption

Colour actually tells remarkably little about an oil's condition. The discolouration depends somewhat on the oil's base structure and additive package - and on the efficiency of the combustion process.
Some oils will discolour very quickly and this is NOT a sign of oil deterioration unless there are other associated and obvious issues present

The hard faced piston rings actually run on the silicon component in the block's structure in any account and not the alloy!

No contaminants in the oil will "assist" the break in process and those of a damaging size (in ppm) are removed by the top quailty oil filters fitted to these engines. Chemicals in the oil will delay or assist the break in process!

The viscosity of the oil will change very little in "normal" use as follows;
a) it may thicken slightly due to deterioration and via its detergency action but very very little during the Porsche recommended oil change cycle

b) it may thin slightly due to high temperature shearing and (heaven forbid) fuel dilution - electronically injected engines are almost foolproof in this regard but excessive idling may cause this condition

The Mobil 1 0w-40 used by Porsche has tended to thin a little initially and then thicken near the end of the Porsche oil change cycle. This is normal and as both Mobil and Porsche intended

In all cases we are talking about very small amounts here ( perhaps 2 to 4% ) and a long way from the designed limits of beyond +/-20% or more!

The Porsche recommended oil change interval can be observed after completing the initial new vehicle recommended oil change

I hope this is of some interest

Regards

Torags

"The viscosity of the oil will change very little in "normal" use as follows;
a) it may thicken slightly due to deterioration and via its detergency action but very very little during the Porsche recommended oil change cycle"

During the course of the break in period, as more contaminants are dropped in the oil with any debri small enough to get thru the filter....

Wouldn't the new chemical composition alter the multi viscosity triggers and the overall viscosity (hence the thickening)? Additionally, I have never seen oil as black as my oil - in iron block engines that I've owned.

I totally agree with the recommended intervals, I think some folks can't think in terms of syn oil. I'm not surprized since the US gets pounded by "oil changers inc" that you should change oil every 3 K. Even new Dino oils don't need that tight a change.

Jeffrey Behr

Doug, VW (or was it Audi?) may do this but Porsche does not. The factory fill is M1 0W-40. I suppose is one likes the idea of casting-sand and engine-machining debris in one's engineoil, leaving the original fill in for 20K-miles is a good idea. Personally, I change oil and filters in new engines the same way the Dems vote in Cook County*--early and often. Even if one ignores the issue of engine break-in on synthetic oil, CLEAN oil is better than dirty oil.


* That's Chicago, home of the long-corrupt Daly political machine.

Doug Hillary

Hi,

Torag - no the "multigrade" composition of the oil will not be affected

Jeffrey - the factory fill formulation is indeed just that - a factory fill oil. Yes it is in barnded M1 0w-40 however it is a specially formulated factory fill product! This formulation is NOT available to other than the factory. And certainly not to Dealers or the Public at large. Its composition is arrived at via the Oil company and the Manufacturer. This is the case I believe for all manufacturers using Mobil synthetic engine oils as a factory fill including MB!

Jeffery your comments are indeed misleading. Nobody suggested leaving oil "contamninated by casting sand etc." in anything! You are wrong.

It is indeed good practice to follow the manufacturers instruction as to the duration the factory fill is left in the engine with any new engine. The Porsche factory's Engineers and the Oil supplier know what they are talking about more than any "outsider".

In over nearly 50 years in this business and having been well trained in Automotive Engineering I have never heard of an engine failing due due to "casting-sand and engine machining debris" damaging an engine - let alone one that has had its engine oil changed when the manufacturer recommended it!!! The M3 BMW had a more complex problem!

I can also tell you Jeffery that some Porsche Alusil engines have in the past suffered thru lack of correct break-in when using factory fill synthetic oils - costing the factory many engines and dollars in the process!!!

Regards

ljugete

Thanks for the good advice Doug!