Bull

I do it because I track the car in the Fall, and my car is driven during the Winter, although much less often than other times of the year. You could leave it 'til Spring if you prefer.

As someone pointed out above, the 15k change interval recommendation by the Factory assumed the cars would be used differently than most of us use our cars.

tbil

Porsche, along with many manufacturers at the time, were promoting their low cost of ownership and increased service intervials as I recall. Wouldn't think oil change frequency to be a very likely cause of warranty issues so no need to "cover their asses".

Best way I know of to determine a good intervial for a particular car / driving is to send a sample of the old oil for analysis. That will tell how broken down the additives are and how much contamination exists.

jhubs

I change oil once a year or every 10K miles whichever comes first. My theory is that the 12 quarts of oil in our air cooled cars allows for a little longer oil life and therefore more miles between changes. When the oil is changed we leave 1.5 qts. of "old" oil in the system otherwise I would go 12K miles.
I know oil life is not the real issue, it's engine life...but it makes sense to me.
Now that I have a 2011 C4S, I change my oil every 18-24 months as I only put around 3k miles a year on it. The water cooled cars run cooler and I feel it OK to do this. I change my own oil because the two times it was done at the dealer, they overfilled the oil by 3/4 to 1 1/4 quarts. There is no dipstick so it is a little touchy to get it just right. Plus, I save $200 and it is very easy to change the oil in this car compared to the 993.

OldGuy

Changing your oil once a year is a good rule of thumb. I got into oil analysis because I raced motocross and Honda oil and Yamalube were $8 a quart when Mobil one was $4 a qt. There was also studies because some of our bikes had the tranny sitting in the same oil as the motor. You didnt want too many friction modifiers in your clutch plates becasue it would cause slippage and thats a no no when your sitting in the gates and the gates drop. So after many many threads and getting guys to do oil analysis and we would pay $100 a pop to send the oil out from our race bikes for analysis alot. Just to see how the motor was breaking down. One thing we found in a study by Ford Motor company and conaco oil was that engine wear decreased as oil aged. That flies in the face of what our dads told us but there seemed to be a viscosity break in of about 1000 miles. So you could baby a motor to death. It came down to 5000 miles a change with EXTREME Conditions warrant changes down to 3 000 miles. Also you want to get rid of nasties sitting in your motor right before putting your car away for winter.
15000 for a GT3 motor thats worth $40-45K seems risky and We got guys at the track changing between sessions. If you are going to change between sessions then send a sample out occasionally to get analysis done on it.
the Bottom line for us racer dudes who spnent ungodlly amounts of money on motors exhausts and everything we could think of ifit made us faster was that Mobil one @$4 a qt is just as good as any
Yama lube at$8 a quart. THat was the bottom ilne

Cincy_Ron

I sent in my last oil change on the Boxster earlier this summer. I let it go wayyyy longer than I ever have. Mileage between change was 15,466 and it was exactly 3 weeks shy of being 2 years between changes. Sent it out to Blackstone Labs in Ft. Wayne Indiana and I think the cost was around $24. I was prepared to get some bad news from them but it was surprisingly good.

I'm coming up on a year in the 993 in November and I'll be just shy of 7,000 miles so I'm going to change it and shoot a sample out to them. Well worth the cost I think...

Here are the results from my 986

TAI2

I change the oil and filters every 6K miles and right before I put it away for the winter (4 months of sitting) if the last change was more than 4K miles ago. I do 6-8 AutoX's per year. Next year I will do both AutoX and DE's and will change every 3 DE's. I do my own changes and I use mix of Bran Penn oils to end up with 15-50.

JDSStudios

This explains why an internal memo was circulating at VW,
saying that oil changes were not to be done sooner than recommended.

At the time I argued with my friend, that worked there, that it was not correct,
and it did not make any sense; maybe I was wrong.

timothymoffat

Interesting Paul (OldGuy), this explains why the dealer kept turning my mother away when I suggested she get an oil change on her new 08 CRV. They said the same thing, don't change the oil too early. All those years of brain washing, slowly washing away.

My 993(s)? Once a year as I cover ~4000miles/year per car.

luft

Guys i change my oil ones a year on 4 Porsche's 3 911's and one 928 S4 only driving 2000 k miles between them. I love my cars and baby them but feel stupid every time i change oil as it is as clean as the new oil i put in. Further every 2 years i use an Indy shop to change oil just for the records. Yes tell me, am i stupid or what. I live in Carefree AZ so good weather year around but being a snow bird in the hot summer the cars a getting a dust cover, air up the tires and go to sleep for 4 months. 2 cents.

pp000830

Air cooled engines expose the oil to much higher temperatures than seen in other cars. My '86 Carrer, when filled with Mobil 1 oil, would use no oil at all until around 5000 miles at which point it would start consuming oil. I inferred from this that at 5000 miles the oil was beginning to no longer maintain its viscosity and was slipping past the rings. So going forward from that point I changed my Carrera's oil at 5K. I have carried over this habit to my 993. To this day I change my 993's oil every 5k miles being careful not to overfill and have never had to top-off the engine oil between changes.
Andy