[968 Cab]

Lots of studies out there now and the opinion are leaning to longer cycle oil changes:

Engine wear actually decreases as oil ages. This has also been substantiated in testing conducted by Ford Motor Co. and ConocoPhillips, and reported in SAE Technical Paper 2003-01-3119. What this means is that compulsive oil changers are actually causing more engine wear than the people who let their engine's oil get some age on it.

Topping up the crankcase is a critical component of extended oil change intervals, and frequent filter changes are most likely the key to extreme-length intervals. The cumulative effect of even minor top-ups, let alone a filter change, substantially increases the longevity of the oil.

Take a read at http://neptune.spacebears.com/cars/stories/mobil1.html



Or do a search over at Rennlist for Doug Hillary "Oil Condition Report" - a 9 part oil condition report spanning 2 years on the 928 forums. You just might save a few $$ and help the environment at the same time while saving your engine!

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[Greimann]

It is nice to see that the 3000 mile oil change is being debunked in more and more discussions. Plain wasteful unless you only drive the car 3000 miles per year.



Being a lubrication professional myself (Castrol Industrial North America) I have looked at lot of discussion about oil (both from industry professionals and wannabes (AKA Amsoil distributors)) and scientific laboratory studies on wear materials, TAN, viscosity shear down ... etc. I have come to some basic personal conclusions about the subject.



1. People love to discuss, figure, argue and ponder the why's and how's about motor oil because it is like gambling where the payoff is going to be 10 to 20 years down the road (if you keep the car that long). You can see no short term benefit so the decision is perceived to be so important that one must spend an extraordinary amount of brain power to make sure you have made the right move. This leads me to point #2.



2. People way overthink this and spend way too much time testing, arguing and figuring it. Mostly because it is entertaining - not that there is anything wrong with that. Discussion and research for the purpose of personal fulfillment is great. Where laboratory oil analysis really matters is in large industrial machines where rebuild costs can run in the millions of dollars, the down time is equally expensive and an oil change costs $10K. In a business, every decision has a dollar value. In a privately owned passenger car, oil changes are cheap! How much was your last fillup at the gas pump?



3. You can sleep soundly at night and still send your kids to college if you change every 5k miles for mostly city driving, 10K miles for mostly freeway driving, or once a year, whichever comes first, (always with a new filter).

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[rustech]

He has spoken <img src="/forum/images/smilies/968/laugh.gif" class="smilie" alt="" />

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[Greimann]

[quote name='rustech' date='Jul 29 2005, 06:45 PM']He has spoken  <img src="/forum/images/smilies/968/laugh.gif" class="smilie" alt="" />

[right][post="8103"]<{POST_SNAPBACK}>[/post][/right][/quote]

So it is written, so it shall be. <img src="/forum/images/smilies/968/smile.gif" class="smilie" alt="" />



You guys take me way to seriously. I am just here for your entertainment.

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[sasilverbullet]

So, what's the interval?



I use Mobil 1 15w-50 and I change the oil and filter at 5k.

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[RPM]

Alright Dave, once and for all, what is the right answer to the "don't switch to synthetic because you will get leaks..." argument...



My car at just over 70k runs great and the PO (I bought the car at 56k) used Castrol GTX 20W-50. It consumes very little oil between changes. I have stayed with that, changing every 4-6k. My local Porsche wrench told me emphatically not to switch.



On my old 944 S2 I used synthetic because the car had always gotten it. Damn think leaked like a Japanese destroyer in 1945, but that was not the oil's fault.



Please don't give me the 'if the synthetic starts leaking then the leak was there all along' jive - my garage floor is dry and I would like it to stay that way.



Speak oh wise one!

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[Greimann]

[quote name='RPM' date='Jul 29 2005, 09:13 PM']Alright Dave, once and for all, what is the right answer to the "don't switch to synthetic because you will get leaks..." argument

.......

Speak oh wise one!

[right][post="8111"]<{POST_SNAPBACK}>[/post][/right][/quote]

Oh paaaahleeese! I'm not that wise. Wise-ass maybe <img src="/forum/images/smilies/968/smile.gif" class="smilie" alt="" />



The reason behind oil leaks is the chemical sympatico between the elastomer oil seal and the chemical (oil) it is trying to contain. When the motor was factory new, the oil seals were just some kind of rubber compound, nothing more. As the motor was put into service, the oil that was first used in the crankcase, and in subsequent oil changes inflitrated the pores of the elastomer seals and became part of the seal's chemistry. Lets say that was "dino" oil for the first 5 years of life. Now a new owner switches to synthetic oil and the seals will attempt to adapt to this new chemistry. They will either shrink or swell with the change in oil that has inflitrated the pores and therefore, perhaps, generating a leak. This is not a given and depends on the history of the vehicle, but it is possible, but not mandatory.

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[Larry Currie]

I think the owner's manuel says every 15,000 miles.

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[sasilverbullet]

Well, the car was using regular dino oil, and I've put about 3k on the Mobil 1 in it and no leaks. It has 141K on it.

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[968 Cab]

3. You can sleep soundly at night and still send your kids to college if you change every 5k miles for mostly city driving, 10K miles for mostly freeway driving, or once a year, whichever comes first, (always with a new filter).

Thanks for the advice Dave!

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[Larry Currie]

I changed from dino to Mobil 1 about 13,000 miles ago at 127,000. No leaks! I'm changing oil annually which is about every 5 to 6 thousand miles. I did it twice a year on the dino oil.

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[968gene]

Dave, Since the lubricant doesn't seem to be changed as often, should consideration be made to change the filter more often than the lube?? It seems that as the quality of synthetics has improved the quality of the filters has diminished a bit. You comments please.

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[Greimann]

There really doesn't seem to be a consensus in the industry on this. Some newer cars that have oil quality monitoring systems can get the oil change intervals up into the 20k to 30k mile ranges, but say nothing about changing the filter sooner. I think it would be safe to say one filter is good for a 10k mile change. If you were going to do oil analysis and push the interval to 20k miles, it might be a good idea to change the filter once during that cycle. Filters are cheap and easy to change. It can't hurt anything to play it safe.

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[968gene]

....agree, if only the filter was an easy spin off/spin on affair. I know there has been a great deal of conversation about the best way to remove the filter, but I'm giving my friend Cliff's advice and try poking a hole in the top and let it drain for a few minutes. This post will probably be followed by one telling me that there is a check valve that will prevent draining, but I'll give it a try anyway. Could it make the mess any worse?

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[Greimann]

There is a check valve that prevents draining. Poking a hole in the filter only allows another source to dribble oil as you wrestle with it.

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[968 Cab]

[quote name='968gene' date='Jul 31 2005, 09:36 AM']....agree, if only the filter was an easy spin off/spin on affair.  I know there has been a great deal of conversation about the best way to remove the filter, but I'm giving my friend Cliff's advise and try poking a hole in the top and let it drain for a few minutes.  This post will probably be followed by one telling me that there is a check valve that will prevent draining, but I'll give it a try anyway.  Could it make the mess any worse?

[right][post="8181"]<{POST_SNAPBACK}>[/post][/right][/quote]



Get a "cap style" filter wrench from Wal Mart ($5 - size #7) that fits over the /top it has a 3/8" drive or 7/8" socket and it is easy to loosen the oil filter - they get pretty tight once seated a few months. Personally, I don't like the screwdriver through the side method as if the filter is really tight, you are looped when you start piercing the can.



As for removing the thing without spilling it all over the PS pump hoses, and maybe even worse, all over the sway bar bracket / bushing, the 968 is much tighter than a 944 or even 951 where you can slip a plastic bag in there and drop the filter into it just as it comes free of the threaded portion. I'm thinking of making a metal pan of some sort to at least divert the spillage away from all the rubber hoses. Anyone had any luck with a method to divert that spillage??



Dave - another product idea for you!

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[flash]

and now thankfully, i don't have this particular problem with the canton racing spin on filter conversion - remove the lid, pull the cartridge, insert new one, put the lid back on

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