Rich9928p

I took an 1100 mile trip to LA and San Diego this past weekend. My GTS consumed less than 1/2 liter of Mobil 1 15W/50 on the trip, which I feel is quite acceptable. I averaged 18.2 mpg at an average speed of 63 MPH.

Many thanks to SoCal 928's Dr. Bob for his hospitality and the other members for meeting us at dinner. Randy, it was a pleasure to stop and say hello again.

Chuck Z

I have had my GTS for 2-1/2 years and have yet to ad oil between oil changes. Granted, there have been no extended runs like what Rich has just completed. But, there have been several 300-500 mile trips with some spirited driving and no consumption issues at all.

Randy V

Good to see you again Rich, and nice to meet Ms. Betsy this time.

Fastest928

We service over 25 GTS's and not one acheives an oil consumption rate that requires no added oil between oil changes. Oil changes are at ~3000 miles using mobil 1.

Highway driving is better, but still no where near as good a non-GTS.

Chuck, you must have one hell of stock GTS to use no oil between changes!

Marc
DEVEK

Chuck Z

Marc,

I too use Mobil 1 in my GTS and it is stock except for an RMB. Perhaps I don't see it because mine will not usually go 3k miles between oil changes. I typically change the oil every eight months or so no matter the mileage. Probably overkill but its cheap insurance. I am super meticulous about my cars and watch the oil level before, during and after trips and it doesn't seem to change.

While building the database on GTSs I would ask people about oil consumption. Most had never heard there was an issue regarding oil consumption and had no idea why I would ask. For the most part I think I got pretty candid responses and there were about as many owners who said their GTS used oil as those that said theirs did not. I should also add that I did not speak to every owner as some of the GTSs in the data base were sitting on dealers lots and I'm sure they wouldn't know. If they did, I'm sure they probably wouldn't have confirmed oil consumption as most people would view it as a problem.

Are you saying that EVERY GTS will use at least some oil?

Jim bailey - 928 International

Chuck in your survey of owners perhaps the question should be " Have you ever checked the oil level ????" It has always seemed unusual to me that the GTS piston lower "oil scraper" ring land has drain holes which normally open to the inside /underside of a piston BUT for this piston are blind do not go all the way through . Basically , once the lower ring grove is filled with oil there is no place for the excess to escape and it makes it's way up past the other rings and is burned . Porsche whose engineering prowess is so often touted and whose reputation is at risk , recommends changing oil every 12 months or 15,000 miles . Oil does not "wear out" it has been around for millions of years much is collected and recycled . It may get contaminated by unburned fuel , water vapors etc. ; if there is much in the way of metal particles moving around you have bigger problems . Changing the oil five times as often as recommended required to maintain the warranty seems to me to be a bit excessive ...... OH right "pay now or Pay later" , " Better safe than sorry ". I also question if these same people change transmission fluid and filter every 6,000 miles (five times the 30,000 recommendation)....timing belts every 10,000 miles , Coolant every five months , brake fluid every five months or for some reason does excessive caution only apply to engine oil ? And no I do not personally wait for 15,000 miles to change oil even though I probably should! I do shower once per day , not five times .....

Drewster67

I may not own a GTS but my S2 uses almost no oil as well.

I'm a true beleiver that the Oil Brand used is most signaificant, for that reason alone, I use Valvoline 20w50.

Jim, I'm not doubting your word on the 15k oil change but, what about viscosity break down?. Does this fall into the water vapor and unburned fuel catagory?.

Chuck Z

Hi Jim,

Jim wrote: Basically , once the lower ring grove is filled with oil there is no place for the excess to escape and it makes it's way up past the other rings and is burned .

So what you're saying is that all GTSs SHOULD use some oil?

Jim also wrote: Changing the oil five times as often as recommended required to maintain the warranty seems to me to be a bit excessive ...... OH right "pay now or Pay later" , " Better safe than sorry ". I also question if these same people change transmission fluid and filter every 6,000 miles (five times the 30,000 recommendation)....timing belts every 10,000 miles , Coolant every five months , brake fluid every five months or for some reason does excessive caution only apply to engine oil ?

No, in my case. In the humid climate of NC, I would rather not risk any sort of moisture problems due to leaving the oil in that long. Nothing to do with any sort of warranty. As for coolant, brake fluid and trans fluid, they all get changed every 2 to 2-1/2 years. The timing belt will get changed every five years regardless of miles. If I waited the recomended intervals on these services these things might never get done. Call me excessive if you wish but I'm thinking its better than the alternative.

Fastest928

Chuck,
there are a few threads on GTS oil consumption, and below is just one thread and my "test" and results!

It is always better to incrase frequency of oil changes in humid environments and where the average oil temp is below 212.....the boilin gpoint of water! If your oil never reaches 212 or greater...then oilreamins in the crankcase!

Regards,
Marc

06-2002 21:21

I found it odd that the same breather system on a stock GT or S4 results in less than 1qt in 5000 miles, however on a GTS, with similar power as a GT or a headered S4 used 1qt every 400-500 miles. Upon consllting with the factory, I learned of the "increased oil retention of the rings and modified pistons" to improve longevity of the no longer manufacturered blocks. I never got a good answer on the redesign of the pistons until I took a GTS apart and found no oil drainback holes typical of std pistons.
Do not be fooled by Vacuum..it is absence of pressure and if pressure cannot "push", then nothing will move.....
I'm very glad that you have low/no oil consumption, but I would be very interested in long term oil consumption.
the reason that Don, myself and others have changed our oiling system is to prevent high rpm oil pumping/flowing out of the valve cover under hard cornering and acceleration.
LEts keep track of that oiling and see if it realy corrects the issue as our GTS also uses 1qt per 400 miles! Soon up for a rebuild at 150K to modify the pistons.
posted 11-13-2002 22:43 I have completed a rebuild of a 93 GTS, utilizing a revised piston oiling system and stock breather hose locations. So far, after 700+ miles, no measurable oil consumption! I will change the oil at 1000 miles and check then, and then go for the 3000 miles zero consumption target using stock breather system! Lets see if the factory "engine conservation program" is right....If so, did I just do a dumb thing or what. Good thing I have a few blocks around. BTW, after 150K miles - ZERO measurable wear on the block down to the 5 digit! Regards,MarcDEVEK--------------------http://www.devek.net Posts: 125 | From: California | IP: Logged |

marc@DEVEK User5789|!!|Rennlist Site SponsorUser # 5789 posted 12-20-2002 13:36 With now over 2500 miles and still the stock oil breather system with modified pistons....and NO MEASURABLE OIL CONSUMPTION! Just like all of the other 6.5 L strokers we have built on S3, S4 or GTS engine!!!! Soon time for the oil change and measure at 3000 miles. Looks like the factory was right after all! MarcDEVEK--------------------http://www.devek.net

Fastest928

..ahhh...that is "water" will remain in the crankcase!

Marc
DEVEK

WallyP

For most 928s, the recommended mileage for oil changes makes no sense. My suggestion is once a year in the fall, and if you are really **** about it, again in the spring.

Jim bailey - 928 International

Water in the oil has little or nothing to do with humidity in the air . The crankcase is sealed only vents to the intake ( positive crankcase ventilation required by law ). The main source is from the combustion of fuel which creates water , very hot water . Blowby past the rings ( going the opposite way of the oil which is being consumed )would include some steam . It is not necessary for the oil to be 212 degrees to boil off the water . Consider for a moment that when my car gets rained upon the rain drops do not last forever ! Just a nice drive with the engine at normal operating temperature will evaporate any water which may have condensed on cold surfaces and allow it to be sucked into the intake and "burned" . All modern oils have many additives including anti-corrosion , anti-foaming , viscosity increasers to cling to metal surfaces . But Oil folklore is much like religion and based on faith . Side note , since 1998 Mack trucks recommends 40,000 mile oil changes or 800 hours for their trucks (yes , they do over 100,000 miles per year).

Fastest928

Last time I built an engine...ahh, a few weeks ago, all crankcase breathers "begin" prior to the throttle body..which is to open to atmosphere. Hmm, maybe the filter is actually a one way valve..

The combustion process produces one gal of water for each gal of gas, of which very little gets into the oil, most goes out the tailpipe!

...if you find a multi grade oil, say a 15-50, that does not end up over time reduced in viscosity to the lowest weight...let us know cause then we can also have prepetual motion machines at our disposal!

So, I am glad that you like running your engine for a year or two on multigrade oil and I hope you enjoy the benefits of running a 10-15 wt oil. Maybe after the oil has been in a street car for a year or two, you can put it in the race car and due to reduced grade, get a few more ponies due to lower pumping losses! Of course, you may have to rebuild the engine a few time per year...hmm...I think that I am on to something here

For me, I will continue to change oil in the 3-5000 mile interval and/or when the oil pressure per temp unit drops.

Good luck
Marc

Marc

Jim bailey - 928 International

Oil breathers , yes there are two ; one has a approximately 12 mm hole the other about 6 mm with hoses plumbed to the intake above the throttle body . So yes it could be possible for some moisture ladened air to enter the crankcase , why it would wish to escapes me . I still maintain that an occasional drive with the engine at operating temperature should purge any condensed water vapors from the crankcase . I find it rather amusing that the advertising claims of "helps prevent viscosity breakdown" or "helps prevent Thermal breakdown " In today's high reving engines " becomes accepted as a statement of fact proving that such breakdown actually does occur . Tying a rope to a pig "helps prevent pigs from flying" but does not prove that pigs can fly . If oil in a Mack truck is usable for up to 40,000 miles , I maintain that pigs do not fly . Porsche recommends every 12 months or 15,000 miles they should know they designed and built it . Obviously more frequently will not hurt the car ( only your wallet ) but that same "logic" can be applied to all recommended service intervals . After all that,I find myself changing oil at about 5,000 mile intervals still three times the minimum .

Doug Hillary

Hi,
My 500hp Detoit Diesel engined trucks have a recommened change interval of 15000kms ( 10k M). I use Mobil Synthetic Delvac 1 5w-40 and with oil analysis I change at about 100000kms ( 62k M) By analysis we know that the oil gets dirty and THICKER not THINNER with use. Most car users waste synthetic oils by changing them too soon. I agree with Jim about change periods in our Sharks
Doug H